Fast channel switching method and apparatus for digital broadcast receiver

ABSTRACT

A fast channel switching method and apparatus for a digital broadcast receiver having a single tuner are disclosed. The fast channel switching method includes setting an ongoing service channel and at least one standby service channel, buffering broadcast data received through the ongoing and standby service channels, outputting the buffered broadcast data of the ongoing service channel, determining whether the ongoing service channel is switched to one of the standby service channels, outputting, if the ongoing service channel is switched to one of the standby service channels, the buffered broadcast data of the switched standby service channel and resetting the ongoing and standby service channels.

CLAIM OF PRIORITY

The present application is a Continuation of U.S. patent applicationSer. No. 11/811,430 filed on Jun. 8, 2007, which claims the benefit ofthe earlier filing date, under 35 U.S.C. §119(a), to Korean PatentApplications filed in the Korean Intellectual Property Office on Jun.13, 2006, and assigned Serial No. 2006-52983, and on Jun. 13, 2006, andassigned Serial No. 2006-52984, the entire disclosure of which arehereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a digital broadcast receiver and, inparticular, to a fast channel switching method and apparatus for adigital broadcast receiver having a single tuner.

2. Description of the Related Art

A digital broadcast receiver is an apparatus that restores originaldigital data from a broadcast signal transmitted by a broadcast station.The digital data is coded and modulated so as to be broadcast in theform of a broadcast signal by the broadcast station. The digitalbroadcast receiver demodulates and decodes the broadcast signal forrecovering the original digital data. The digital broadcast receiver isprovided at least with a tuner, a demodulator, and a decoder.

Digital broadcast systems are classified into a digital multimediabroadcast (DMB) system or a digital video broadcasting (DVB) system.These digital broadcast systems provide a plurality of service channelsin a frequency band and each service channel is structured withmultiplexed sub-channels of video, audio, and program information data.

Current mobile devices are typically powered by multimedia processorsthat support various multimedia functions including digital broadcastreception. With the integration of the multimedia functions, the mobiledevices are becoming much complex in physical configuration andexecution procedures. Here, the mobile devices include mobile phones,Smartphone, laptop computers, Personal Digital Assistants (PDAs), etc.

A digital broadcast channel is divided into a number of service channelsfor delivery of audio, video, data, and multimedia, such that abroadcast receiver scan the broadcast channel for retrieving the servicechannels. Since the digital broadcast channel consists of a plurality ofservice channels, channel navigation for searching a target channel maybe a cumbersome labor.

In digital broadcasting, particularly, the digital data is highlycompressed and thus it takes a considerable amount of time for a screento become stable after switching to a service channel. This is unlikeswitching channels in an analog broadcasting system. This is because ofa processing delay caused by demodulation and decoding of the broadcastsignals of the selected service channel. Accordingly, the broadcast datacorresponding to the delay time are lost or an out-of time image isdisplayed on the screen.

In the case of DVB, data bursts come up every 1 to 4 seconds.Accordingly, if a channel switching event occurs while receiving aservice channel, the screen shows nothing before the data burst assignedto the target channel comes up, resulting in inconvenient tosubscribers.

SUMMARY OF THE INVENTION

The present invention has been made in an effort to solve the aboveproblems, by providing a fast channel switching method and apparatus fora digital broadcast receiver that are capable of reducing channelswitching delay.

It is another aspect, a fast channel switching method and apparatus fora digital broadcast receiver that are capable of reducing channelswitching delay by buffering broadcast data on neighbor service channelsof an ongoing service channel and displaying, when a channel switchingevent occurs, the buffered broadcast data.

It is another aspect, there is provided a fast channel switching methodand apparatus for a digital broadcast receiver that are capable ofreducing channel switching delay by buffering broadcast data on theongoing service channel and at least one favorite service channels anddisplaying, when the favorite channel is selected, the bufferedbroadcast data.

It is another aspect, there is provided a fast channel switching methodand apparatus for a digital broadcast-enabled mobile phone that arecapable of reducing channel switching delay by buffering broadcast dataon at least one the neighbor service channels of an ongoing servicechannel and displaying, when the neighbor service channel is selected,the buffered broadcast data on the selected neighbor service channel.

It is another aspect, there is provided a fast channel switching methodand apparatus for a digital broadcast enable mobile phone that arecapable of reducing channel switching delay by buffering broadcast dataon the ongoing service channel and at least one favorite servicechannels and displaying, when the favorite channel is selected, thebuffered broadcast data.

In accordance with another aspect of the present invention, the above isaccomplished by a fast channel switching apparatus for a digitalbroadcast receiver. The fast channel switching apparatus includes atuner for receiving service channels of a frequency channel; a broadcastdemodulator for demodulating the service channels and outputting anongoing service channel and at least one standby service channel amongthe service channels, a storage for storing broadcast data of theongoing and standby service channels output from the broadcastdemodulator into corresponding buffers and reading out the broadcastdata buffered in a buffer of the ongoing service channel, a decoder fordecoding the broadcast data read out of the storage and output video andaudio data, a display for displaying the video data output from thedecoder and a speaker for outputting the audio data output from thedecoder, wherein the storage reads out, when the ongoing service channelis switched to one of the standby service channels, the broadcast databuffered for the standby service channel.

In one aspect, the fast channel switching apparatus further includes achannel switching controller for resetting, when the ongoing servicechannel is switched to another service channel, the broadcastdemodulator and storage with new ongoing and standby service channels.

In one aspect, the broadcast demodulator includes a demodulator fordemodulating the service channels and an identifier filter set withidentifiers of the ongoing and standby service channels for filteringthe demodulated broadcast data of the ongoing and candidate servicechannels.

In one aspect, the identifier is a program identifier (PID).

In one aspect, the storage includes a plurality of buffers for bufferingthe broadcast data of the ongoing and standby service channels, a firstselector for writing the broadcast data of the ongoing and standbyservice channels into corresponding buffers and a second selector forreading out the broadcast data of the ongoing service channel bufferedin the corresponding buffer.

In one aspect, the standby service channels include a lower neighborservice channel and an upper neighbor service channel of the ongoingservice channel in channel number.

In one aspect, the channel switching controller controls, when theongoing service channel is switched to one of the standby servicechannels, the storage to read out the buffered broadcast data of thestandby service channel as a new ongoing service channel, controls thebroadcast demodulator and the storage, if the standby service channel isthe upper neighbor service channel, to delete the PID of the lowerneighbor service channel and add a PID of the upper neighbor servicechannel of the new ongoing service channel and controls the broadcastdemodulator and the storage, if the standby service channel is the lowerneighbor service channel, to delete the PID of the upper neighborservice channel of the ongoing service channel and add the PID of thelower neighbor service channel of the new ongoing service channel.

In one aspect, the standby service channels include favorite servicechannels selected in consideration of a user preference.

In one aspect, the channel switching controller controls, when theongoing service channel is switched to one of the favorite servicechannels, the storage to read out the buffered broadcast data of thefavorite service channel as a new ongoing service channel and controls,if the ongoing service channel is one of the favorite service channel,the broadcast demodulator and the storage to maintain the ongoingservice channel as a favorite service channel.

In one aspect, the standby service channels include neighbor servicechannels of the ongoing service channel and favorite service channelsselected in consideration of a user preference.

In accordance with another aspect of the present invention, the above afast channel switching apparatus for a digital broadcast receiver isdisclosed. The fast channel switching apparatus includes a tuner forreceiving service channels of a frequency channel, a broadcasterdemodulator for demodulating the service channels, a demultiplexer setwith identifiers of an ongoing service channel and at least one standbyservice channel for demultiplexing broadcast data of the ongoing andstandby service channels service channels, a storage for buffering thebroadcast data output from the demultiplexer into buffers correspondingto the service channels and reading out the broadcast data bufferedwithin the buffer of the ongoing service channel, a broadcast decoderfor decoding the broadcast data read out of the storage, a display fordisplaying video data output from the decoder and a speaker foroutputting audio data output from the decoder, wherein the storage readsout, when the ongoing service channel is switched to one of the standbyservice channels, the broadcast data buffered for the standby servicechannel.

In one aspect, the fast channel switching apparatus further includes achannel switching controller for resetting, when the ongoing servicechannel is switched to another service channel, the demultiplexer andstorage with new ongoing and standby service channels.

In one aspect, the demultiplexer checks an identifier contained a headerof a packet carrying the broadcast data of the service channel, andperforms, if the identifier is one of the identifier set in thedemultiplexer, demultiplexing on the broadcast data so as to outputvideo and audio data.

In one aspect, the identifier is a program identifier (PID).

In one aspect, the storage includes a plurality of buffers for bufferingthe broadcast data of the ongoing and standby service channels, a firstselector for writing the broadcast data of the ongoing and standbyservice channels into corresponding buffers and a second selector forreading out the broadcast data of the ongoing service channel bufferedin the corresponding buffer.

In one aspect, the standby service channels include a lower neighborservice channel and an upper neighbor service channel of the ongoingservice channel in channel number.

In one aspect, the channel switching controller controls, when theongoing service channel is switched to one of the standby servicechannels, the storage to read out the buffered broadcast data of thestandby service channel as a new ongoing service channel, controls thedemultiplexer and the storage, if the standby service channel is theupper neighbor service channel, to delete the PID of the lower neighborservice channel and add a PID of the upper neighbor service channel ofthe new ongoing service channel, and controls the demultiplexer and thestorage, if the standby service channel is the lower neighbor servicechannel, to delete the PID of the upper neighbor service channel of theongoing service channel and add the PID of the lower neighbor servicechannel of the new ongoing service channel.

In one aspect, the standby service channels include favorite servicechannels selected in consideration of a user preference.

In one aspect, the channel switching controller controls, when theongoing service channel is switched to one of the favorite servicechannels, the storage to read out the buffered broadcast data of thefavorite service channel as a new ongoing service channel; and controls,if the ongoing service channel is one of the favorite service channel,the demultiplexer and the storage to maintain the ongoing servicechannel as a favorite service channel.

In one aspect, the standby service channels include neighbor servicechannels of the ongoing service channel and favorite service channelsselected in consideration of a user preference.

In accordance with another aspect of the present invention, a fastchannel switching method for a digital broadcast receiver is disclosed.The fast channel switching method includes setting an ongoing servicechannel and at least one standby service channel, buffering broadcastdata received through the ongoing and standby service channels,outputting the buffered broadcast data of the ongoing service channel,determining whether the ongoing service channel is switched to one ofthe standby service channels, outputting, if the ongoing service channelis switched to one of the standby service channels, the bufferedbroadcast data of the switched standby service channel and resetting theongoing and standby service channels.

In one aspect, the standby service channels include an upper neighborservice channel and a lower neighbor service channel of the ongoingservice channel in channel number.

In one aspect, resetting the ongoing and standby service channelsincludes setting the switched standby service channel as a new ongoingservice channel, deleting, if the switched service channel is the upperneighbor service channel of the previous ongoing service channel, thelower neighbor service channel of the previous ongoing service channelfrom the standby service channels, deleting, if the switched servicechannel is the lower neighbor service channel of the previous ongoingservice channel, the upper neighbor service channel of the previousongoing service channel from the standby service channels.

In one aspect, buffering broadcast data received through the ongoing andstandby service channels includes checking an identifier attached to thebroadcast data, determining whether the identifier is of the ongoingservice channel or one of standby service channels and startingbuffering, if the identifier is of the ongoing service channel or one ofthe standby service channels, the broadcast data.

In one aspect, the standby service channels include favorite servicechannels selected in accordance with a user preference.

In one aspect, resetting the ongoing and standby service channelsincludes setting, if the ongoing service channel is switched to anon-standby service channel, the non-standby service channel as a newongoing service channel, stopping, if the previous ongoing servicechannel is not one of the favorite service channels, buffering thebroadcast data of the previous ongoing service channel and maintaining,if the previous ongoing service channel is one of the favorite servicechannels, buffering the broadcast data of the previous ongoing servicechannel as one of the standby service channels.

In one aspect, buffering broadcast data received through the ongoing andstandby service channels includes checking an identifier attached to thebroadcast data, determining whether the identifier is of the ongoingservice channel or one of standby service channels and startingbuffering, if the identifier is of the ongoing service channel or one ofthe standby service channels, the broadcast data.

In one aspect, the standby service channels include neighbor servicechannels of the ongoing service channel and favorite service channelsselected in consideration of a user preference.

In one aspect, resetting the ongoing and standby service channelsincludes setting the switched standby service channel as a new ongoingservice channel, determining, if the switched service channel is aneighbor service channel of the previous ongoing service channel,whether the switched service channel is the lower or upper neighborservice channel, deleting, if the switched service channel is the upperneighbor service channel of the previous ongoing service channel, thelower neighbor service channel of the previous ongoing service channelfrom the standby service channels, deleting, if the switched servicechannel is the lower neighbor service channel of the previous ongoingservice channel, the upper neighbor service channel of the previousongoing service channel from the standby service channels, determining,if the switched service channel is not a neighbor service channel of theprevious ongoing service channel, whether the switched service channelis one of the favorite service channels, determining, if the switchedservice channel is one of the favorite service channels, whether theprevious ongoing service channel is one of the favorite servicechannels, stop, if the previous ongoing service channel is not one ofthe favorite service channels, buffering the broadcast data of theprevious ongoing service channel, and maintain, if the previous ongoingservice channel is one of the favorite service channels, buffering thebroadcast data of the previous ongoing channel as one of the standbyservice channels.

In one aspect, resetting the ongoing and standby service channelsincludes setting the switched standby service channel as a new ongoingservice channel, determining, if the switched service channel is aneighbor service channel of the previous ongoing service channel,whether the switched service channel is the lower or upper neighborservice channel; determining, if the switched service channel is theupper neighbor service channel, whether the lower neighbor servicechannel of the previous ongoing service channel is one of the favoriteservice channels, stopping, if the lower neighbor service channel of theprevious ongoing service channel is not one of the favorite servicechannels, the buffering of the broadcast data of the lower neighborservice channel; determining whether the upper neighbor service channelof the witched service channel is one of the favorite service channel,setting, if the upper neighbor service channel of the switched servicechannel is not one of the favorite service channel, the upper neighborservice channel as a standby service channel; determining, if the lowerneighbor service channel is the lower neighbor service channel, whetherthe upper neighbor service channel of the previous ongoing servicechannel is one of the favorite service channels; stopping, if the upperneighbor service channel of the previous ongoing service channel is notone of the favorite service channels, the buffering of the broadcastdata of the upper neighbor service channel; determining whether thelower neighbor service channel of the switched service channel is one ofthe favorite service channel; setting, if the lower neighbor servicechannel of the switched service channel is not one of the favoriteservice channel, the lower neighbor service channel as a standby servicechannel; determining, if the switched service channel is not a neighborservice channel of the previous ongoing service channel, whether theprevious ongoing service channel is one of the favorite servicechannels; stopping, if the previous ongoing service channel is not oneof the favorite service channels, the buffering of the broadcast data ofthe previous ongoing service channel; and maintaining, if the previousongoing service channel is one of the favorite service channels, thebuffering of the broadcast data of the previous ongoing service channelsas the favorite service channel.

In accordance with another aspect of the present invention, a mobilephone is disclosed that includes a radio frequency unit for radiocommunication of the mobile phone; a digital broadcast receivercomprising a tuner for receiving service channels of a frequencychannel, a broadcast demodulator for demodulating the service channelsand outputting an ongoing service channel and at least one standbyservice channels among the service channels, a storage for storingbroadcast data of the ongoing and standby service channels output fromthe broadcast demodulator into corresponding buffers and reading out thebroadcast data buffered in a buffer of the ongoing service channel, adecoder for decoding the broadcast data read out of the storage andoutput video and audio data, a controller for controlling the broadcastdemodulator to demodulate the broadcast data, the storage to bufferbroadcast data of the ongoing and standby service channels and outputthe buffered broadcast data of the ongoing service channel, and theradio frequency unit to process calls in a broadcast mode; a display fordisplaying the video data output from the decoder; and a speaker foroutputting the audio data output from the decoder.

In one aspect, the controller controls the storage to read out, when theongoing service channel is switched to one of the standby servicechannels, the buffered broadcast data of the switched standby servicechannel, and resets the broadcast demodulator and the storage withidentifier of new ongoing and standby service channels.

In one aspect, controller controls the display to display, when anincoming call is received in the broadcast mode, an incoming call alertmessage with caller information on the display.

In one aspect, the controller controls the radio frequency unit totransmit, when an outgoing call event occurs, the outgoing call throughan antenna.

In accordance with another aspect of the present invention, a mobilephone is disclosed that includes a radio frequency unit for radiocommunication of the mobile phone; a digital broadcast receivercomprising a tuner for receiving service channels of a frequencychannel, a broadcaster demodulator for demodulating the servicechannels, a demultiplexer set with identifiers of an ongoing servicechannel and at least one standby service channel for demultiplexingbroadcast data of the ongoing and standby service channels servicechannels, a storage for buffering the broadcast data output from thedemultiplexer into buffers corresponding to the service channels andreading out the broadcast data buffered within the buffer of the ongoingservice channel, a broadcast decoder for decoding the broadcast dataread out of the storage, a controller for controlling the demultiplexerto demultiplex the broadcast data, the storage to buffer broadcast dataof the ongoing and standby service channels and output the bufferedbroadcast data of the ongoing service channel, and the radio frequencyunit to process calls in a broadcast mode, a display for displaying thevideo data output from the decoder and a speaker for outputting theaudio data output from the decoder.

In one aspect, the controller controls the storage to read out, when theongoing service channel is switched to one of the standby servicechannels, the buffered broadcast data of the switched standby servicechannel, and resets the broadcast demodulator and the storage withidentifier of new ongoing and standby service channels.

In one aspect, the controller controls the display to display, when anincoming call is received in the broadcast mode, an incoming call alertmessage with caller information on the display.

In one aspect, the controller controls the radio frequency unit totransmit, when an outgoing call event occurs, the outgoing call throughan antenna.

In accordance with another aspect of the present invention, a fastchannel switching apparatus of a broadcast receiver is disclosed. Thefast channel switching apparatus includes a tuner for receiving servicechannels of a frequency channel, a broadcast demodulator fordemodulating the service channels and outputting an ongoing servicechannel and at least one standby service channel identified by presetidentifiers, a storage unit for storing broadcast data of the ongoingand standby service channels output from the broadcast demodulator incorresponding buffers and reading out the broadcast data if the bufferset with the identifier of the ongoing service channel, a broadcastdecoder for decoding the broadcast data read out from the storage unit;a display for displaying the video data output from the decoder and aspeaker for outputting the audio data output from the decoder, whereinthe fast channel apparatus sets, if a channel switching commandindicating a service channel is detected, the service channel as a newongoing service channel and playing the broadcast data buffered in thebuffer assigned the identifier of the new ongoing service channel.

In accordance with another aspect of the present invention, a fastchannel switching apparatus of a broadcast receiver is disclosed. Thefast channel switching apparatus includes a tuner for receiving servicechannels of a frequency channel, a broadcast demodulator fordemodulating the service channels; a demultiplexer set with identifiersof an ongoing service channel and at least one standby service channelfor demultiplexing broadcast data received with the identifiers, astorage unit for buffering the broadcast data output from thedemultiplexer in buffers set with corresponding identifiers and readingout the broadcast data buffered in the buffer assigned the identifier ofthe ongoing service channel, a broadcast decoder for decoding thebroadcast data read out from the storage unit, a display for displayingvideo data output from the decoder, and a speaker for outputting audiodata output from the decoder, wherein the storage unit reads out, when achannel switching command is detected, the broadcast data buffered inthe buffer assigned the identifier of switched service channel.

In accordance with another aspect of the present invention, a fastchannel switching method for a broadcast receiver is disclosed. The fastchannel switching method includes checking service channels receivedthrough a frequency channel on the basis of identifiers attached to theservice channels, buffering ongoing and standby service channels, ofwhich identifiers are set as ongoing and standby service channelidentifiers, in corresponding buffers, respectively, playing the ongoingservice channel, switching, if a channel switching command is detected,the ongoing service channel to the a new ongoing service channelindicated by the channel switching command, playing the new ongoingservice channel buffered in the corresponding buffer and updating theongoing and standby service channel identifiers.

In accordance with another aspect of the present invention, a mobilephone is disclosed that includes a radio frequency unit for processingincoming and outgoing radio signals, a digital broadcast receivercomprising a tuner for receiving service channels of a frequency channelgiven for a broadcast system, a broadcast demodulator set with servicechannel identifiers for demodulating the service channels received withthe service channel identifiers, a storage unit having a plurality ofbuffers for buffering the service channels output from the broadcastdemodulator with reference to the service channel identifiers, and abroadcast decoder for decoding the service channel selectively read outfrom the storage unit. a controller for controlling to play the ongoingservice channel, buffer the ongoing and standby service channels in thecorresponding buffers, set the broadcast demodulator and storage unitwith the service channel identifiers, switch, if a channel switchingcommand being detected, the ongoing service channel to a new ongoingservice channel indicated by the channel switching command, play the newongoing service channel, update the ongoing and standby service channelidentifiers, reset the broadcast demodulator and storage unit with theupdated ongoing and standby service channel identifier, and processincoming and outgoing calls while playing the ongoing service channel, adisplay for displaying video data decoded from the ongoing servicechannel; and a speaker for outputting audio data decoded from theongoing service channel.

In accordance with another aspect of the present invention, a mobilephone is disclosed that includes a radio frequency unit for processingincoming and outgoing radio signals, a digital broadcast receivercomprising a tuner for receiving service channels of a frequency channelgiven for a broadcast system, a broadcast demodulator for demodulatingthe service channels output from the tuner, a demultiplexer set withservice channel identifiers for demultiplexing the service channels withreference to the service channel identifiers, a storage unit having aplurality of buffers for buffering the service channels output from thedemultiplexer on the basis of the service channel identifiers andreading out broadcast data buffered in the buffer assigned theidentifier of the ongoing service channel, and a broadcast decoder fordecoding the broadcast data output from the storage unit, a controllerfor controlling to play the ongoing service channel, buffer the ongoingand standby service channel in the corresponding buffers, set thebroadcast, update next service channel identifier at every data burstsfor the service channels, switch, if a channel switching command beingdetected, the ongoing service channel to a new ongoing service channelindicated by the channel switching command, play the broadcast datastored in the buffer assigned the service channel identifier of the newongoing service channel, and process incoming and outgoing calls whileplaying the ongoing service channel; a display for displaying video datadecoded from the ongoing service channel; and a speaker for outputtingaudio data decoded from the ongoing service channel.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other, features and advantages of the present inventionwill be more apparent from the following detailed description inconjunction with the accompanying drawings, in which:

FIG. 1 is a block diagram illustrating a configuration of a digitalbroadcast receiver including a fast channel switching method andapparatus according to an exemplary embodiment of the present invention;

FIG. 2 is a block diagram illustrating a configuration of the broadcastdemodulator 120 of FIG. 1;

FIG. 3 is a block diagram illustrating a configuration of the storageunit 130 of the digital broadcast receiver of FIG. 1;

FIG. 4 is a block diagram illustrating a configuration of broadcastdecoder of a DVB-H receiver according to an exemplary embodiment of thepresent invention;

FIGS. 5A to 5F are diagrams illustrating a frame format of a DVB-Hsystem.

FIG. 6A is a diagram illustrating a conventional frame format adapted toa time slicing scheme.

FIGS. 6B to 6D are diagrams illustrating a frame format for a fastchannel switching method according to an exemplary embodiment of thepresent invention;

FIG. 6E is a diagram illustrating a frame format for a fast channelswitching method according to another exemplary embodiment of thepresent invention;

FIG. 7 is a flowchart illustrating a fast channel switching methodaccording to an exemplary embodiment of the present invention;

FIG. 8 is a flowchart illustrating a broadcast playback procedure of thefast channel switching method of FIG. 7;

FIG. 9 is a flowchart illustrating a channel switching procedure of afast channel switching method of FIG. 7;

FIG. 10 is a flowchart illustrating a broadcast playback procedure ofthe fast channel switching method according to another embodiment of thepresent invention;

FIG. 11 is a flowchart illustrating a channel switching procedure of afast channel switching method according to another exemplary embodimentof the present invention;

FIG. 12 is a flowchart illustrating a broadcast playback procedure of afast channel switching method according to another exemplary embodimentof the present invention;

FIG. 13 is a flowchart illustrating a channel switching procedure of afast channel switching method according to another exemplary embodimentof the present invention;

FIG. 14 is a flowchart illustrating a standby service channel settingprocedure of the fast channel switching method according to an exemplaryembodiment of the present invention;

FIG. 15 is a flowchart illustrating a broadcast playback procedure of afast channel switching method according to another exemplary embodimentof the present invention;

FIG. 16 is a flowchart illustrating a standby channel bufferingprocedure of FIG. 15 when no favorite service channels are set;

FIG. 17 is a flowchart illustrating a standby channel bufferingprocedure of FIG. 15 when favorite channels are set.

FIG. 18 is a flowchart illustrating a channel switching procedure offast channel switching method according to another exemplary embodimentof the present invention;

FIG. 19 is a block diagram illustrating a digital broadcast receiverincluding a fast channel switching apparatus and method according to anexemplary embodiment of the present invention;

FIG. 20 is a block diagram illustrating a mobile terminal equipped witha DVB-H receiver including a fast channel switching apparatus accordingto another exemplary embodiment; and

FIG. 21 is a block diagram illustrating a mobile terminal equipped witha DVB-T receiver including a fast channel switching apparatus accordingto another exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Exemplary embodiments of the present invention are described withreference to the accompanying drawings in detail. The same referencenumbers are used throughout the drawings to refer to the same or likeparts. For the purposes of clarity and simplicity, detailed descriptionsof well-known functions and structures incorporated herein may beomitted to avoid obscuring the subject matter of the present invention.

In order to help understanding the present invention, generaldescriptions on the components of the digital broadcast systemsincluding DVB, such as burst channel time and a number of servicechannel to be buffered. Nevertheless, it would be recognized by thoseskilled in the art that the present invention is not limited thereto butcan be modified within the scope of the appended claims.

In the following embodiments, a digital broadcast receiver adopting thefast channel switching method and apparatus of the present inventionbuffers broadcast data on the ongoing service channel and at least oneother service channel in preparation for an expected channel switching.Digital broadcast systems can be generally classified into DigitalMultimedia Broadcasting (DMB) or a Digital Video Broadcasting (DVB). TheDVB is further classified into DVB-terrestrial (DVB-T) and DVB-Handheld(DVB-H). Particularly, the DVB-H transmits broadcasts data in the formof IP datagrams as data bursts in small timeslots. In the followingembodiment, the fast channel switching technique of the presentinvention is described with regard to a DVB-H receiver. However, thepresent invention can be adopted to both the DVB and DMB.

A “Channel” denotes a frequency bandwidth given for the broadcast systemand the broadcast channel consists of a plurality of time-divisionmultiplexed “service” channels that are distinguished by a programidentifier or product identifier (PID). An “event” denotes a programprovided through each service channel.

In the following embodiment, a term “physical channel” isinterchangeably used with the broadcast channel, and each time-divisionmultiplexed timeslot are called “service channel. A digital broadcastsystem transmits a plurality of service channels in one physicalchannel. The physical channel means a frequency band set for a tunersuch that the service channels are identified by PID in the frequencyband of the physical channel. In the following embodiment, the digitalbroadcast receiver includes a single tuner that switches between theservice channels.

An “ongoing service channel” denotes a service channel that is selectedso as to be on-air. A “standby service channel” denotes a servicechannel that is likely to be selected at an expected channel switch. A“previous service channel” is the service channel that was on-air rightbefore switching to the current ongoing service channel. A “neighborservice channel” is a service channel positioned right before or afterthe ongoing service channel in time line. An “upper neighbor servicechannel” is the neighbor service channel having a channel number greaterthan that of the ongoing service channel, and a “lower neighbor servicechannel” is the neighbor service channel having a channel number lessthan that of the ongoing service channel. A “preference service channel”denotes a service channel that is frequently selected by a subscriber.The neighbor service channels and preference service channels arerepresented by “buffering service channels” on which broadcast data arebuffered while the broadcast data of the ongoing service channel aredisplayed on a screen.

FIG. 1 is a block diagram illustrating a configuration of a digitalbroadcast receiver adopting the fast channel switching method andapparatus according to an exemplary embodiment of the present invention.

Referring to FIG. 1, the digital broadcast receiver includes acontroller 100, a tuner 110, a broadcast demodulator 120, a storage unit130, a broadcast decoder 140, a display unit 150, a speaker 155, amemory unit 160, and a key input unit 170.

The controller 100 controls general operations of the digital broadcastreceiver. The key input unit 170 generates a key signal in response to auser key input and transfers the key signal to the controller 100. Thekey signal includes a channel selection command, channel navigationcommand, and playback command, etc. The controller 100 controls thebuffering of broadcast data on at least one predetermined servicechannel while playing the broadcast data of an ongoing service channeland plays, if the buffering service channel is selected, the bufferedbroadcast data. The memory unit 160 includes a program memory forstoring application programs for performing service channel switchingand buffering the broadcast data on the predetermined buffering servicechannel, and a data memory for storing the buffered data. The controller100 analyzes the user commands input through the key input unit 170 andcontrols the operation of the digital broadcast receiver in response tothe user's commands. The controller 100 controls the operation of thedigital broadcast receiver in response to the command input providedthrough the key input unit 170.

The tuner 110 sets the burst time (timeslot) and switches on for thedata bursts corresponding to service channels selected by a subscriber.The broadcast demodulator 120 performs demodulation on the broadcastsignals output from the tuner 110. The broadcast demodulator 120 candemodulate broadcast signals for multiple service channels. The storageunit 130 buffers the broadcast data of the ongoing service channel andat least one preset standby service channel. The broadcast decoder 140is implemented with a video decoder and audio decoder such that thevideo decoder decodes video data and delivers the decoded video data tothe display unit 150 and the audio decoder decodes audio data anddelivers the decoded audio data to the speaker 155.

The broadcast demodulator 120 and broadcast decoder 140 can beimplemented in different structures according to the type of the digitalbroadcast system. The digital broadcast receiver can be one of DMB,DVB-T, and DVB-H receivers.

The broadcast data of the DMB and DVB are broadcasted in the form of aMotion Picture Experts Group 2 transport stream (MPEG2-TS) packet streamand each MPEG2-TS packet consists of a header and payload. The packetheader contains a PID as an identifier assigned to a service channelsuch that the digital broadcast receiver can recognize the servicechannel referring to the PID.

The payload of the MPEG2-TS packet for the DMB or DVB-T is filled withthe broadcast data, and the payload of the MPEG2-TS packet (DVB-H IPencapsulated packet) for DVB-H is filled with Internet Protocol (IP)datagrams. In the case of DVB-T or DMB, the broadcast demodulator 120 isimplemented to demodulate broadcast data of a service channel, and thebroadcast decoder 140 is implemented with a demultiplexer for decodingthe demodulated broadcast data and video and audio decoders.

In the case of DVB-H, the broadcast demodulator 120 is implemented witha demodulator for demodulating the broadcast data, a PID filter forfiltering the broadcast data of a selected service channel, and ademodulation controller for controlling the cooperation of thedemodulator and the tuner 110. Also, the broadcast decoder 140 includesa protocol processing unit for processing IP information and video andaudio decoders.

In this embodiment, the digital broadcast receiver plays the broadcastdata stream on the ongoing service channel while buffering at least onestandby service channel, which is likely to be selected at an expectedchannel switching, and plays, when switched to the standby servicechannel, the broadcast data buffered on the standby service channel,whereby it is possible to reduce the channel switching delay.Accordingly, seamless channel switching can be achieved.

In this embodiment, the digital broadcast receiver buffers broadcastdata on at least one preset service channel, e.g. a neighbor servicechannel, in order to reduce processing delay at a next channel switchingoperation. The channel switching can be performed in two kinds ofmanners. That is, the user may select a service channel by navigatingthe service channels using up/down keys or by pressing a specific numberkey corresponding to a service channel. In the case of the channelswitching with navigation key manipulation, the service channelsneighboring the ongoing service channel are preferably selected as thestandby service channels. In the case of the channel switching withpreset channel number key, favorite service channels, e.g. the servicechannels registered by the user or frequently played, are set for thestandby service channels.

In the navigation key-based channel switching method, the user navigatesthe service channels for selecting a service channel using thenavigation keys. In this case, the digital broadcast receiver buffersthe broadcast data on the ongoing service channel and neighbor servicechannels that are positioned right before and after the ongoing servicechannel in channel numbers. The broadcast demodulator 120 demodulatesthe broadcast data on the ongoing and neighbor service channels, and thestorage unit 130 buffers the demodulated broadcast data received on thedemodulated ongoing service channel and at least one neighbor servicechannel. The broadcast decoder 140 decodes the demodulated broadcastdata of the ongoing service channel and outputs decoded video and audiodata through the display unit 150 and the speaker 155, while bufferingthe broadcast data on the neighbor service channels. A size of thestorage 130 can be changed in consideration of the channel switchingpattern of the user. If a channel switching signal is input through anup/and down key while playing the broadcast data on the ongoing servicechannel, the controller 100 detects the switching signal and deliversthe broadcast data of the service channel buffered in the storage unit130 to the broadcast decoder 140. The broadcast decoder 140 decodes thebroadcast data of the selected service channel and outputs the decodedvideo and audio data through the display unit 150 and the speaker 155without recognition of the change of the ongoing broadcast channel.Here, upon detecting the switching signal input, the control unit 100controls the broadcast demodulator 120 and storage unit 130 so as toprepare next channel switching operation.

In this switching method, the user can register favorite servicechannels so as to navigate to the registered service channels when thechannel switch signal is input through the up/down key. At this time,the controller 100 controls the storage unit 130 to buffer the broadcastdata on service channels neighboring the ongoing service channel in alist of the favorite service channels.

In the number key-based channel switching method, the service channelswitching is triggered by a specific number key input through the keyinput unit 170. In this case, the digital broadcast receiver buffers thebroadcast data received through the ongoing service channel and at leastone favorite service channel as the standby service channel. Thebroadcast demodulator 120 demodulates the broadcast data on the ongoingand standby service channel and the storage unit 130 buffers thedemodulated broadcast data on the ongoing and standby service channels.The broadcast decoder 140 decodes the broadcast data of the ongoingservice channel output from the storage unit 130 and outputs video andaudio data decoded from the broadcast data through the display unit 150and speaker 155. Buffer size of the storage unit 130 can be set inconsideration of the time taken for channel switching. If a channelselection signal is input through the key input unit 170, the controller100 detects the channel selection signal and determines the channelnumber corresponding to the channel selection signal that matches one ofthe standby service channels buffered in the storage unit 130. If theselected service channel matches one of the standby service channels,the controller 100 directs the storage unit 130 to deliver the bufferedbroadcast data of the selected service channel to the broadcast decoder140 such that the broadcast decoder 140 decodes the broadcast data ofthe changed service channel and outputs the decoded video and audio datathrough the display unit 150 and the speaker 155. Next, the controller100 analyzes the user's preferences on the service channels, e.g.frequency of channel selection, and determines the standby servicechannels of which data to be buffered. The information on the servicechannels to be buffered is provided to the broadcast demodulator 120 andthe storage unit 130 such that the broadcast demodulator 120 and thestorage unit 130 prepare for the next channel switching operation.

As described above, the digital broadcast receiver having a signal tuneraccording to the first embodiment of the present invention buffersbroadcast data on at least one neighbor service channel of the ongoingservice channel while playing the broadcast data received through theongoing service channel, and displays, when the neighbor service channelis selected, the buffered broadcast data without switching delay.

According to a second embodiment of the present invention, a digitalbroadcast receiver having a signal tuner buffers broadcast data on atleast one favorite service channel frequently selected by the user whileplaying the broadcast data received through the ongoing service channel,and displays, when the favorite channel is selected, the bufferedbroadcast data without switching delay.

In the fast channel switching methods according to the first and secondembodiments, when the ongoing service channel is switched to a presetstandby service channel, the digital broadcast receiver plays bufferedstandby service channel broadcast data such that the channel switchingis performed seamlessly with minimized data processing delay.

In the description of the digital broadcast receiver of FIG. 1 a DVB-Hreceiver is assumed.

FIG. 2 is a block diagram illustrating a configuration of the broadcastdemodulator 120 of FIG. 1, and FIGS. 5A to 5F are diagrams illustratinga frame format of a DVB-H system.

Referring to FIG. 5A to 5F, DVB-H uses MPEG2-TS packets. Each TS packethas a length of 188 bytes consisting of a 4-byte header and a 184 bytepayload. The packet header contains packet synchronization informationand packet identifier (PID). The PID is a channel identifier and can beused for identifying data contained in the payload. The payload consistsof multi protocol encapsulation (MPE) sections. Each MPE sectionincludes a table identifier (table_ID), MPE forward error correction(MPE-FEC) information for correcting errors of the received data,information for slicing the received data in time. Each MPE contains atleast one IP datagram. In FIG. 5A to 5F, IPv6 datagram is depicted as anexample. The IP datagram includes an IP version information, source IPaddress, and destination address. The IP datagram consists of userdatagram protocol (UDP) units and each UDP unit includes port addressesof the transmitter and receiver (Scr Prt and Dst Prt). The UDP unitcontains FLUTE/ALC units and a real-time transport protocol (RTP) unit.The FLUTE/ALC unit includes the Electronic Service Guide (ESG) and filesand the RTP unit includes audio and video data.

Referring to FIG. 2, the broadcast demodulator 120 is connected to thetuner 110 and includes an analog/digital (A/D) converter 210, ademodulation module 220, a PID filter 230, and a demodulation controller240. The tuner 110 includes a phase-locked loop (PLL) circuit forgenerating a frequency for the physical channel, a mixer for mixing thereceived signal and the signal generated by the PLL, and a band-passfilter for passing the frequency of the physical channel.

The demodulation controller 240 controls the tuner 200 on the basis ofcontrol signals received from the control unit 100 so as to set thephysical channel frequency and the PID of the service channel selectedby the PID filter 230. At this time, the controller 100 analyzesinformation such as Program Specific Information/Stream Information(PSI/SI) and Session Description Protocol (SDP) that are processed bythe broadcast demodulator and the broadcast decoder 140 and checks thePIDs of the ongoing and standby service channels. Accordingly, thebroadcast data on the service channels having the PIDs are played orbuffered. In this embodiment, the controller 100 can control the servicechannel switching operation.

The A/D converter 210 converts the output of the tuner 110 into digitaldata, the demodulation module 220 demodulates the digital data outputfrom the A/D converter 210. The demodulation module 220 can beimplemented with an Orthogonal Frequency Division Multiplexing (OFDM) orCoded OFDM (COFDM) demodulator. The data demodulated by the demodulationmodule 220 can be a TS packet 5A.

The TS packet contains a PID as an identifier for identifying theservice channel. The PID filter 230 passes the data having the PID ofthe selected service channel from the demodulated IP datagram andtransports the PSI/SI to the controller 100. The TS packet passed to thePID filter 230 may include the MPE-FEC and time slicing information inFIG. 5B.

If the TS packet contains the MPE section (FIG. 5B), the demodulationcontroller 240 performs time slicing control on the received burst data.That is, the demodulation controller 240 controls power supplied to thetuner 110 and demodulation module 220 on the basis of the time slicinginformation contained in the MPE section. The time slicing informationcontains information on the burst-on time of the selected and bufferedservice channel such that the demodulation controller 240 can controlthe power supplied to the tuner 110 and the demodulation module 220 inthe burst data durations of the ongoing and standby service channels onthe basis of the time slicing information. The demodulation controller240 also can perform the MPE-FEC function on the data of the selectedand buffered broadcast data output from the PID filter 230 using the MPEsection information.

As described above, the demodulation controller 240 controls the tuner110 on the basis of the channel control data output from the controller100 to set the selected service channel and sets the PID filter 230 withthe PIDs of the ongoing and standby service channels. The demodulationcontroller 240 controls the timing slicing operation for reducing thepower consumption of the digital broadcast receiver on the basis of theMPE section information (FIG. 5B) and performs the MPE-FEC function forimproving reception rate by compensating the reception errors. At thistime, the data output from the demodulation controller 240 can be an IPdatagram (FIG. 5C).

The broadcast demodulator 120 delivers the IP datagram having astructure shown in FIG. 5C to the storage unit 130, and the storage unit130 stores the broadcast data on the standby service channels intorespective buffers while outputting the broadcast data of the ongoingservice channel. The broadcast decoder 140 processes the IP datagramsdelivered from the storage unit 130 and outputs the video and audiodata.

FIG. 3 is a block diagram illustrating a configuration of the storageunit 130 of the digital broadcast receiver of FIG. 1.

Referring to FIG. 3, the storage unit 130 includes a plurality ofbuffers 331, 332, . . . , 33N for buffering the broadcast data of theongoing and standby service channels while playing the broadcast dataoutput from the broadcast demodulator 120. The number of the buffers isgreater than the number of the standby service channels. For example, ifthe number of standby service channels is 2, the number of buffers N isequal to or greater than 3. This is because the broadcast data on theongoing service channel is buffered together with the broadcast data onthe standby service channels. Also, the buffers 331 to 33N can beimplemented as such number of the service channels in the broadcastchannel and corresponding service channels. The storage unit 130 alsoincludes a first selector 320 connected to input nodes of the buffers331 to 33N and a second selector 340 connected to output nodes of thebuffers 331 to 33N. The controller 100 generates selection controlsignals for delivering the broadcast data of the ongoing and standbyservice channels to the corresponding buffers. The first selector 320delivers the broadcast data output from the broadcast demodulator 120 tocorresponding buffers under the control of the controller 100, and thesecond selector 340 delivers the broadcast data output from a buffermatched to the ongoing service channel to the broadcast decoder 140under the control of the controller 100. The first selector 320 can beimplemented with a demultiplexer, and the second selector 340 can beimplemented with a multiplexer.

The buffers 331 to 33N are provided as such number of the servicechannels such that the buffers 331 to 33N are mapped to the respectiveservice channels. The controller 100 generates control signals forcontrolling the delivery of the broadcast data of the ongoing andstandby service channels to the respective buffers 331 to 33N. The firstselector 320 selects the broadcast data output from the broadcastdemodulator 120 and forwards the broadcast data to the correspondingbuffer under the control of the controller 100. The second selector 340selects the broadcast data output from the buffer of the ongoing servicechannel and forwards the broadcast data to the broadcast decoder 140.The storage unit 130 can be implemented as a random access memory thatassigns buffering regions having predetermined sizes. In this case, thefirst selector 320 is implemented with a write address generator, andthe second selector 340 is implemented with a read address generator.That is, the buffering regions are assigned as such number of theongoing and standby service channels and matching the ongoing andstandby service channels to the specific buffering regions. If thebroadcast data of the standby service channel is output from thebroadcast demodulator 120, the controller 100 generates a write addresssuch that the broadcast data are stored in the region of the writeaddress. Also, the controller 100 generates a read address of thebuffering region and informs the second selector 340 of the readaddress. When the storage 130 is implemented with a memory, the firstand second selectors 320 and 240 are implemented with the write and readaddressing mechanism, respectively.

The operation of the above structured storage unit 130 is describedhereinafter. The controller 100 knows the PID of the ongoing servicechannel and the states of the buffers 331 to 33N buffering the broadcastdata of the ongoing and standby service channel. Accordingly, thecontroller 100 checks the PID of the ongoing service channel andcontrols the first selector 320 to store the received broadcast data tothe corresponding buffer. The controller 100 also controls the secondselector 340 to deliver the broadcast data of the service channel to thebroadcast decoder 140 on the basis of the PID. The sizes of the buffers331 to 33N can be set in consideration of the time to be taken forprocessing channel switching operation, i.e. obtaining and processingthe broadcast data. In the case of DVB-H, since the burst interval is 1to 4 seconds, the size of each buffer is preferably set for bufferingthe broadcast data during this time interval.

The controller 100 also controls the first selector 320 in accordancewith the standby service channel designation schemes. In the case thatthe neighbor service channels are designated for the standby servicechannels, the controller 100 controls the first selector 320 to bufferthe broadcast data on the ongoing service channel and neighbor servicechannels within corresponding buffers 331 to 33N. The neighbor servicechannels are service channels neighboring the ongoing service channelupper and lower in channel number. If the neighbor service channels arethe lower and upper service channels right before and after the ongoingservice channel, buffering is carried out in an order of the lowerneighbor service channel, ongoing service channel, and upper neighborservice channel. In this case, the controller 100 controls the firstselector 320 to deliver broadcast data of the lower neighbor servicechannel, ongoing service channel, and upper neighbor service channels tothe corresponding buffers in a sequential order.

In a case that the frequently selected service channels are designatedfor the standby service channels, the controller 100 sets a number ofthe candidate channels and checks the service channels having high userpreferences such that the first selector 320 writes the broadcast dataof the ongoing service channel and the service channels having higheruser preferences to the corresponding 331 to 33N.

In a case that the standby service channels are selected in accordancewith both the neighbor channel-based and favorite channel-based standbyservice channel designation schemes, the controller 100 creates afavorite service channel list and designates the neighbor favoriteservice channels for the standby service channels such that the firstselector 320 writes the broadcast data of the ongoing and neighborfavorite service channels to the corresponding buffers 331 to 33N.

The controller 100 also controls the second selector 340 to output thebroadcast data of the ongoing service channel to the broadcast decoder140.

If a channel switching signal is detected for switching to one of thestandby service channel while playing the broadcast data on the ongoingservice channel, the controller 100 controls the second selector 340 tooutput the broadcast data buffered on the switched standby servicechannel to the broadcast decoder 140.

If the channel switching is completed, the controller 100 resets thestandby service channels with reference to the new ongoing servicechannel. That is, the standby service channels are reset in accordancewith the standby service channel designation scheme, i.e. neighbor-basedor favorite channel-based standby service channel designation scheme.Next, the controller 100 resets the broadcast demodulator 120 with thePIDs of the new standby service channels (in the case of DVB-H, thebroadcast demodulator 120 is set with the PIDs and the broadcastdemodulator sets the PID filter 230 with the PIDs of the standby servicechannels.), and controls the first selector 320 to write the broadcastdata of the standby service channels into the corresponding buffers ofthe storage unit 130.

In another aspect, since the controller 100 has the information on thePID of the ongoing and standby service channels and the status of thebuffers 331 to 33N set up with the PIDs, the controller 100 checks thePIDs of the received broadcast data and controls the first selector 320to store the broadcast data in the corresponding buffers on the basis ofthe PIDs. The controller 100 also controls the second selector 340 toread out the broadcast data having the PID of the ongoing channels tothe broadcast decoder 140. The size of each buffer is set up inconsideration of the time to be taken for obtaining the broadcast dataof the service channel switched thereto after channel switching istriggered. In the case of DVB-H, since the burst interval is 1 to 4seconds, the size of each buffer is preferably set up to buffer anamount of broadcast data corresponding to 4 seconds.

In another aspect, since the controller 100 has the information on thePID of the ongoing and standby service channels and the status of thebuffers 331 to 33N set up with the PIDs, the controller 100 checks thePIDs of the received broadcast data and controls the first selector 320to store the broadcast data in the corresponding buffers on the basis ofthe PIDs. The controller 100 also controls the second selector 340 toread out the broadcast data having the PID of the ongoing channels tothe broadcast decoder 140. Accordingly, the second selector 340 selectsan output buffer that is storing the broadcast data of the ongoingservice channel, and reads out the broadcast data stored in the bufferto the broadcast decoder 140 under the control of the controller 100.The first selector 320 forwards the broadcast data output from thebroadcast demodulator 120 to the storage unit so as to be stored in therespective buffers identified by PID.

If the channel switching is completed in the above manner, thecontroller 100 controls the first selector 320 to select the broadcastdata of the new ongoing and standby service channels to be buffered. Thesecond selector 340 reads out the broadcast data buffered in the ongoingservice channel buffer of storage unit 130 to the broadcast decoder 140under the control of the controller 100, in the broadcast playback mode.While playing the broadcast data of the ongoing service channel, thefirst selector 320 selects the broadcast data of the standby servicechannels such that the broadcast data of the standby service channelsare buffered. In the case that the favorite channel-based servicechannel designation scheme is adopted, the controller 100 controls thefirst selector 320 to select the broadcast data of the favorite servicechannels such that the broadcast data of the favorite service channelsare stored in the corresponding buffers. In the case that theneighbor-based service channel designation scheme is adopted, thecontroller 100 controls the first selector 320 to select the broadcastdata of the neighbor service channels such that the broadcast data ofthe neighbor service channels are stored in the corresponding buffers.

If a channel switching command is detected in the broadcast playbackmode, the controller 100 controls the second selector 340 to read outthe broadcast data, stored in the buffer mapped to the switched-toservice channel to the broadcast decoder 140 and resets the standbyservice channels of which broadcast data are to be buffered.

After the channel switching is completed, the controller 100 can changethe buffering order of the service channels. That is, the bufferingorder of the service channels is set in accordance of the new standbyservice channels. Even if the buffering order of the service channels isnot changed, the buffering performance is not changed. That is, sincethe buffering is performed in a predetermined order (sequential order ordirectional order), the broadcast data of a standby service channel isupdated every burst interval. For this reason, the buffering order hasno effect to the buffering efficiency.

FIG. 4 is a block diagram illustrating a configuration of broadcastdecoder of a DVB-H receiver according to an exemplary embodiment of thepresent invention.

Referring to FIG. 4, the broadcast decoder includes a protocolprocessing unit 410, a video decoder 430, and an audio decoder 440.

The protocol processing unit 410 decapsulates hierarchal protocol dataunits and processes the payload of each protocol data unit on the basisof protocol information. The video decoder 430 decodes video data fromthe protocol processing unit 410 and outputs the decoded video data tothe display unit 150.

The audio decoder 440 decodes audio data from the protocol processingunit 410 and outputs the decoded audio data to the speaker 155.

The protocol processing unit 410 includes an IP decapsulator 411, a UDPdecapsulator 413, a FLUTE deliverer 415, an RTP deliver 417, and ademultiplexer 419.

The IP decapsulator 411 extracts an IP datagram (FIG. 5C) from the MPEsection (FIG. 5B) and decapsulates the IP datagram so as to check thesource and destination IP addresses.

The UDP decapsulator 413 extracts a UDP unit (FIG. 5E) from the IPdatagram and decapsulates the UDP unit to check the source anddestination port numbers.

If the data carried by the UDP unit is FLUTE/ALC protocol data, the UDPdecapsulator 413 transports the FLUTE/ALC protocol data to the FLUTEdeliverer 415. If the data carried by the UDP unit is RTP data, the UDPdecapsulator 413 transports the RTP data to the RTP deliverer 417.

The FLUTE/ALC protocol data may include ESG or other type of data suchas XML, SDP, HTML, JPG, and POL. The RTP data may include the audio andvideo data. The RTP deliverer 417 sends the video and audio data to thedemodulator 419. The demodulator 419 demodulates the video and audiodata, and outputs the demodulated video and audio data to the respectivevideo and audio decoder 430 and 440, respectively.

The protocol processing unit 410 operates under the control of thecontroller 100. The controller 100 can integrate an ESG engine (XMLengine and ESG decoder), an SDP parser, and a PSI/SI decoder. Thecontroller 100 also can integrate a protocol information controller andmanager for controlling the protocol process and management. Thecontroller 100 processes the protocol information and data received fromthe protocol processing unit 410. That is, the controller 100 analyzesthe PSI/SI table (NIT, SDT, and EIT) extracted by the broadcastdemodulator 120 so as to check the PSI/SI according to the MPEG-2 andDVB-SI standards, parses the ESG data received from the protocolprocessing unit 410, and then controls the overall operation of thedigital broadcast receiver on the basis of these information. Theservice channels, ESG per service channel, and audio and video data areidentified using the PID, IP, and port information. That is, the PSI/SIand SDP is provided with tables defining information on the servicechannel identifiers, audio and video identifiers, and ESG identifiers.The controller 100 can identify the service channels, audio data, videodata, and ESG data with reference to the decoding result of the PSI/SIand the SDT. The controller 100 can include the protocol processing unit410.

The demodulated video and audio data output from the protocol processingunit 410 are delivered to the video decoder 430 and the audio decoder440. The video decoder 430 decodes the video data and displays thedecoded data on the display unit 150 (not shown) in the form of visualimage, and the audio decoder 440 decodes the audio data and outputs thedecoded audio data through the speaker (not shown) in the form ofaudible sound. The video decoder 430 can be implemented with a H.264decoder or MPEG series decoder, and the audio decoder 440 can beimplemented with an AAC decoder.

The above-structured digital broadcast receiver buffers the broadcastdata on the service channels in addition to the ongoing service channelin preparation for an expected channel switching, whereby it is possibleto smoothly switch between service channels without processing delay.The service channel switching operation of the above-above structureddigital broadcast receiver is described hereinafter. The channelswitching operation is described with a DVB-H receiver as an exemplarydigital broadcast receiver.

FIGS. 6A to 6B are diagrams illustrating a format of a time frameadopted to the fast channel switching method and system according to anexemplary embodiment of the present invention.

DVB-H system uses a time slicing mechanism to reduce the average powerconsumption of the broadcast receiver such that the broadcast receiveris switched on while receiving the burst for the ongoing servicechannel. FIG. 6A shows a time frame stream in which each time frameconsists of 6 timeslots corresponding to six service channels CH1 toCH6. In FIG. 6A, CH3 is an ongoing service channel, for example. Thetime duration in which the broadcast data are received is called bursttime, and the timeslots corresponding to the CH1, CH2, and CH4 to CH6,are called burst-off time. As shown in FIG. 6A, each service channel isperiodically repeated such that the broadcast receiver can predict theburst time of the ongoing service channel. Of course, the broadcastreceiver can predict the burst time of another channel too. Assumingthat 6 service channels are multiplexed in a time frame and the bursttime for each service channel is 1 second, the broadcast data of theongoing service channel is received every 6 seconds. Since the broadcastreceiver knows the burst time and burst-off time as well as channelnumbers for the timeslots, the demodulation controller 240 can controlthe receiver to receive the broadcast data at the burst time of theongoing service channel in accordance with time slicing mechanism. Inthe same manner, the demodulation controller 240 can control thereceiver to receive the broadcast data at the burst times of the standbyservice channels.

FIG. 6A shows a frame format adapted to a fast channel switching methodaccording to an exemplary embodiment of the present invention.

Referring to FIG. 6A, as the service channel CH3 is the ongoing servicechannel, for purposes of illustration, channels CH2 and CH4 areneighboring the ongoing service channel CH3 and are selected as thestandby service channels according to the neighbor channel-based standbyservice channel designation scheme. In this case when a channelswitching signal is input for switching to the CH2, for example, whileplaying the ongoing service channel CH3, the broadcast receiver cannotreceive the broadcast data of the service channel before the next bursttime of the service channel CH2 comes up. Accordingly, delay of thedisplay stream occurs on the display unit 150.

However, in accordance with the principles of the instant invention, thebroadcast receiver buffers the broadcast data received at the bursttimes of standby service channels CH2 and CH4. Accordingly, when thechannel switching signal is input for switching to the CH2 channel, thebroadcast receiver plays the data buffered during the burst time of thestandby service channel CH2 without waiting for the next burst time.Hence, there is no delay of the display stream.

Also, the broadcast receiver can be implemented so as to buffer thebroadcast data of all service channels. In this case, if ongoing servicechannel is changed, the broadcast receiver plays the broadcast databuffered for the switched-to service channel. Accordingly, the channelswitching can be performed in seamless manner without a time gap betweenthe old and new ongoing service channel screen images.

Typically, the channel switching occurs frequently for the neighborservice channel, i.e. a lower numbered neighbor service channel or uppernumbered neighbor service channel. That is, the probability of thechannel switching to one of the neighbor service channels CH2 and CH4while watching the ongoing service channel CH3 is high. By buffering thebroadcast data of the service channels that have the high selectionprobabilities at the next channel switch and playing the bufferedbroadcast data of the selected service channel, it is possible to playthe broadcast data of the newly selected channel without significantswitching delay. The number of the standby service channels of whichbroadcast data to be buffered can be changed. For example, the neighborservice channels CH1, CH2, CH4, and CH5 can be designated as the standbyservice channels. Of course, the number of the buffers 331 to 33N shouldbe increased in proportional with the number of the standby servicechannel.

If the upper neighbor service channel CH4 is selected while the playingthe broadcast data of the ongoing service channel CH3 (FIG. 6B), theservice channel CH4 become the new ongoing service channel. Accordingly,the old ongoing service channel, CH3, and the service channel CH5neighboring the new ongoing service channel CH4 are set as the newstandby service channel, as shown in FIG. 6C, such that the broadcastdata of the standby service channels CH3 and CH5 are buffered while thebroadcast data of the ongoing service channel CH4 are played on thescreen. In order to buffer the broadcast data on the standby servicechannels, the broadcast receivers should switch on at the burst times ofthe standby service channel in addition to the ongoing service channel.

FIG. 6E shows a frame format adapted to a fast channel switching methodaccording to another exemplary embodiment of the present invention.Referring to FIG. 6E. the service channel CH4 is a the ongoing servicechannel and the service channels CH2 and CH6 are designated as thestandby service channel of which broadcast data are buffered while thebroadcast data of the ongoing service channel are played. In thisembodiment, the standby service channels are selected on the basis ofthe user preference which can be represented by selection frequency ortotal played time of the service channel. Also, the standby servicechannels can be selected from a favorite service channels registered bythe user. In FIG. 6E, the service channels CH2 and CH6 of whichprobabilities to be selected are higher than other service channels suchthat the broadcast data of the service channels CH2 and CH6 are bufferedwhile playing the broadcast data of the ongoing service channel CH4.

FIG. 7 is a flowchart illustrating a fast channel switching methodaccording to an exemplary embodiment of the present invention. In thisembodiment, the standby service channels are neighbor service channelsof the ongoing service channel as shown in FIGS. 6B to 6D.

Referring to FIG. 7, when a channel selection signal is input throughthe key input unit 170, the controller 100 checks the ServiceDescription Table (SDT) of the PSI/SI or ESG data and sets the frequencyof the physical channel with reference to the SDT (S510) and then sets aPID of the selected service channel (S520). Next, the controller 100sets PIDs of the standby service channels (S530). That is, when aservice channel is selected by a user, the controller 100 sets thefrequency of the physical channel and then sets the ongoing and standbyservice channels. The standby service channels are set by checking thePIDs of the standby service channels and assigning buffers for bufferingthe broadcast data of standby service channels within the storage unit130. The standby service channels are represented by the neighborservice channels of the ongoing service channel or the user preferencechannels. The standby service channels can be preset or determined whenthe ongoing service channel is selected.

In the case of the DVB-H receiver, the controller 100 generates acontrol signal for setting the frequency for the service channel, thedemodulation controller 240 sets the tuner 110 with the physical channelfrequency. Next, the demodulation controller 240 configures the codingscheme, coding rate, and guard interval of the demodulation module 220.The demodulation controller 240 also configures the PID filter 230 withthe PID of the ongoing service channel. At this time the controller 100also sets the PIDs of the standby service channels in addition to thatof the ongoing service channel.

If an ongoing service channel is selected, the controller 100 determinesthe physical channel of the ongoing service channel and the standbyservice channels through steps 510 to 530. Next, the controller 100operates in a broadcast playback mode (S540). In the broadcast playbackmode, the broadcast demodulator 120 converts the output of the tuner 110into digital data, performs OFDM (or COFDM) demodulation on the digitaldata, and filters the broadcast data having the PID of the ongoingservice channel. If the PID of the broadcast data matches that of theongoing service channel, the broadcast data are buffered within thecorresponding buffer in the storage unit 130. The broadcast data ofwhich PID does not match, the broadcast data are blocked. That is, thedemodulation controller 240 controls the tuner 110 and the demodulationmodule 220 switch-on at the burst times of the ongoing and standbyservice channels in accordance with the time slicing scheme and performsthe MPE-FEC on the demodulated broadcast data so as to output IPdatagram (FIG. 5C). The storage unit 130 stores the IP datagramsreceived through the ongoing and standby service channels withincorresponding buffers under the control of the controller 100. Thestorage unit 130 outputs the IP datagrams to the broadcast decoder 140such that the broadcast decoder 140 decodes the IP datagrams and outputsthe video and audio data decoded from the IP datagrams to the displayunit 150 and the speaker 155. Such operations are performed at the bursttimes of the ongoing and standby service channels, and the tuner 110 andthe broadcast demodulator 120 switch off during the burst off time.These processes are repeated until the broadcast playback mode ends.

FIG. 8 is a flowchart illustrating a broadcast playback procedure of thefast channel switching method of FIG. 7.

Referring to FIG. 8, if broadcast data are received (S611), thecontroller 100 determines whether a PID contained in the broadcast datais identical with the PID of the ongoing service channel (S613). If thereceived broadcast data have the PID of the ongoing service channel, thecontroller 100 controls the decapsulating an IP datagram from thereceived broadcast data (S615) and extracts video and audio data fromthe IP datagram (S617). Next, the controller 100 controls the decodingof the video and audio data (S619) and outputs the decoded video andaudio data through the display unit 150 and the speaker 155 (S621). Thatis, the controller 100 controls to decapsulate, if a received TS packethas the PID assigned to the ongoing service channel, the IP datagramfrom the TS packet, extract the video and audio data from the IPdatagram, and play the extracted video and audio data.

If the PID of the received broadcast data is not identical with the PIDassigned to the ongoing service channel at step S613, the controller 100determines whether the PID of the received broadcast data is identicalwith one of the PIDs assigned to the standby service channels (S631). Inthis embodiment, the standby service channels are the neighbor servicechannels of the ongoing service channel. If the PID of the receivedbroadcast data is identical with one of the PIDs of the standby servicechannels, the controller 100 determines whether the PID is of the upperneighbor service channel or the lower neighbor service channel (S633).If the PID is of the upper neighbor service channel, the controller 100controls the buffering of the IP datagram within an upper neighborservice channel buffer (S635). Otherwise, the buffering of the IPdatagram within a lower neighbor service channel buffer (S637). Forexample, assuming that the ongoing service channel is CH3 as in FIG. 6Band the broadcast data contains the PID assigned for the service channelCH4, the controller 100 controls the storage unit 130 to buffer thebroadcast data within a buffer assigned for the service channel CH4. Ifthe broadcast data contains the PID assigned for the service channelCH2, i.e. the lower neighbor service channel of the ongoing servicechannel CH3, the controller 100 controls the storage unit 130 to bufferthe broadcast data within a buffer assigned for the service channel CH2.Although two neighbor service channels, i.e., the upper and lowerneighbor service channels are designated as the standby service channelsof which broadcast data are to be buffered, the number of standbyservice channel can be changed. For example, more than two servicechannels (for example, CH6, CH1, CH2 and/or CH4, CH5) can be designatedas the standby service channel.

The controller 100 detects whether a channel switching signal forswitching to one of the standby service channel is input while playingthe broadcast data of the ongoing service channel and buffering thebroadcast data of the standby service channel (S623). If a channelswitching signal for switching to standby service channel is detected,the controller 100 switches to the selected standby service channel. Ifa channel switching signal is not detected, the controller 100determines whether a broadcast mode termination signal is input (S625).If a broadcast mode termination signal is input, the controller 100 endsthe reception of the broadcast data.

Thus, the controller 100 controls the playing of the broadcast datareceived through the ongoing service channel while buffering thebroadcast data of the upper and lower neighbor service channel as thestandby service channels, such that the buffered broadcast data are usedwhen one of the neighbor service channels is selected in accordance withthe channel switching signal.

At step S540 (FIG. 7), the controller 100 controls the playing thebroadcast data of the ongoing service channel and buffer the neighborservice channels of the ongoing service channel (S540). If a channelswitching signal for switching to a standby service channel is input bya navigation key (channel up/down or number key) while playing thebroadcast data of the ongoing service channel and buffering thebroadcast data of the standby service channels, the controller 100performs a channel switching procedure (S550) and then returns to thebroadcast playback procedure for playing the broadcast data of the newongoing service channel (S540).

FIG. 9 is a flowchart illustrating a channel switching procedure of afast channel switching method shown in FIG. 7.

Referring to FIG. 9, if the channel switching occurs, the controller 100sets the switched service channel as a new ongoing service channel andchanges its buffer from a standby service channel buffer to an ongoingservice channel buffer (S651) such that the buffered broadcast data areplayed as of the ongoing service channel. Accordingly, the broadcastdecoder 140 decodes the broadcast data of the new ongoing servicechannel without delay of the data stream.

Next, the controller 100 determines whether the new ongoing servicechannel is an upper-numbered service channel to the previous ongoingservice channel (S653). If the new ongoing service channel is anupper-numbered service channel to the previous ongoing service channel,the controller 100 withdraws the PID assigned for the previouslower-numbered service channel (S655) and sets a PID of anupper-numbered neighbor service channel of the new ongoing servicechannel as the PID of a standby service channel (S657). That is, if thenew ongoing service channel is an upper-numbered service channel to theprevious ongoing service channel, the controller 100 sets the upper andlower neighbor service channels of the new ongoing service channel asnew standby service channels.

On the other hand, if the new ongoing service channel is alower-numbered service channel to the previous ongoing service channel,the controller 100 withdraws the PID assigned for the previousupper-numbered service channel (S659) and sets a PID of a lower-numberedneighbor service channel of the new ongoing service channel as the PIDof a standby service channel (S661). That is, if the new ongoing servicechannel is a lower-numbered service channel to the previous ongoingservice channel, the controller 100 sets the upper and low neighborservice channels of the new ongoing service channel as new standbyservice channels.

Concerning the example of FIG. 6B, if the service channel CH4 isselected while playing the broadcast data of the service channel CH3 andbuffering the broadcast data of the neighbor service channels CH2 andCH4, the controller 100 recognizes that the selected channel is theupper neighbor service channel of the ongoing service channel CH3 atstep S653, withdraws the PIDs of the lower and upper neighbor servicechannel at step S655, and sets the PIDs of the new standby servicechannels CH3 and CH5 neighboring the new ongoing service channel CH4 forbuffering the broadcast data thereon. If the service channel CH2 (lowerchannel) is selected while playing the broadcast data of the servicechannel CH3 and buffering the broadcast data of the neighbor servicechannels CH2 and CH4, the controller 100 recognizes that the selectedchannel is the lower neighbor service channel of the ongoing servicechannel at step S653, withdraws the PIDs of the lower and upper neighborservice channels CH3 and CH5 at step S659, and sets the PIDs of the newstandby service channels CH1 and CH3 neighboring the new ongoing servicechannel CH2 for buffering the broadcast data thereon at step S661.

After the new standby service channels are set with their PIDs, thebroadcast demodulator 120 performs demodulation on the broadcast data ofthe new ongoing and standby service channels with reference to the theirPIDs, and the storage unit 130 reassigns the buffers for buffering thebroadcast data of the new ongoing and standby service channels. At thistime, the controller 100 changes the buffer of the previous standbyservice channel that is selected by channel switching operation into aplayback buffer for the ongoing service channel, such that the bufferedbroadcast data is played without processing delay before the next bursttime of the new ongoing service channel comes up. After channelswitching is completed, the controller 100 performs the broadcastplayback procedure at step S540 of FIG. 7.

The channel switching operation of the broadcast receiver in thebroadcast mode is described with reference to FIGS. 1 to 4. If a channelswitching signal for switching to a standby service channel is detected,the controller 100 controls the storage unit 130 to change the buffer ofthe selected standby service channel into a playback buffer such thatthe broadcast data buffered in the buffer are read out. That is, thecontroller 100 controls the second selector 340 to read the buffer ofthe selected standby service channel and deliver the broadcast data readout from the buffer to the broadcast decoder 140. At this time, thebroadcast decoder 140 continues decoding the broadcast data withoutrecognition of the channel switch. Accordingly, a seamless channelswitching is performed without delay of the playback stream.

Before the next data burst of the new ongoing service channel isreceived, the buffered broadcast data are played, such that the buffersize depends on the number of the service channels and the length of thetimeslot. Typically, the burst cycle is 1 to 4 seconds and the buffers331 to 33N are determined in consideration with the burst cycle. Duringthe playback of the buffered broadcast channel, the controller 100resets the PIDs of the ongoing and standby service channels andreconfigures the buffers for the new ongoing and standby servicechannels. Preferably, the buffer size is set to contain an amount of thebroadcast data sufficient to be played before the next data burst of thenew ongoing service channel is received.

During the playback of the buffered broadcast data, the controller 100determines whether the new ongoing service channel is an upper-numberedservice channel to the previous ongoing service channel. If the newongoing service channel is an upper-numbered service channel to theprevious ongoing service channel, the controller 100 withdraws the PIDassigned for the previous lower-numbered service channel and sets thePID of an upper-numbered neighbor service channel of the new ongoingservice channel as the PID of a standby service channel. If the newongoing service channel is a lower-numbered service channel to theprevious ongoing service channel, the controller 100 withdraws the PIDassigned for the previous upper-numbered service channel and sets a PIDof a lower-numbered neighbor service channel of the new ongoing servicechannel as the PID of a standby service channel.

For example, if the service channel CH4 is selected while playing thebroadcast data of the service channel CH3 and buffering the broadcastdata of the neighbor service channels CH2 and CH4, the controller 100generates a control signal for resetting the ongoing and standby servicechannels. Upon receiving the control signal, the broadcast demodulator120 discards the PIDs set for the PID filter 230 and resets the PIDfilter 230 with the PIDs of the new ongoing service channel (CH4) andthe new standby service channels (CH3 and CH5). If the service channelCH2 is selected while playing the broadcast data of the service channelCH3 and buffering the broadcast data of the neighbor service channelsCH2 and CH4, the controller 100 generates a control signal for resettingthe ongoing and standby service channels. Upon receiving the controlsignal, the broadcast demodulator 120 discards the PIDs set for the PIDfilter 230 and resets the PID filter 230 with the PIDs of the newongoing service channels (CH2) and the new standby service channels (CH1and CH 3).

The controller 100 controls the broadcast demodulator 120 to output thebroadcast data having the PIDs of the ongoing and standby servicechannels to the storage unit 130 such that the storage unit 130 buffersthe broadcast data to the buffers corresponding to the ongoing andstandby service channels.

If the ongoing service channel is switched in this manner, the broadcastdemodulator 120 is set with the PIDs of the new ongoing service channelsand the new standby service channels neighboring the ongoing servicechannel, and the buffers 331 to 33N are set to buffer the broadcast dataidentified with the PIDs such that the storage unit 130 buffers thebroadcast data output from the broadcast demodulator 120 within thecorresponding buffers and reads out the broadcast data of the ongoingservice channel. Accordingly, when the ongoing service channel isswitched to one of the standby service channels, the broadcast receiverplays the buffered broadcast data of the switched-to service channeluntil its next data burst is received, resulting in smooth channelswitching without processing delay.

In the former embodiments, the fast channel switching method andapparatus of the present invention have been implemented with theneighbor channel-based standby service channel designation scheme. Inother embodiments, the fast channel switching method and apparatus ofthe present invention are implemented with a favorite channel-basedstandby service channel designation scheme.

It is assumed that the broadcast receiver has the same structure of FIG.1 and is a DVB-H receiver characterized with the structures of FIGS. 2to 4. The main procedure for processing channel switching is identicalwith that in FIG. 7 except for the broadcast playback procedure (S540)and the channel switching procedure (S550).

FIG. 10 is a flowchart illustrating a broadcast playback procedure ofthe fast channel switching method according to another embodiment of thepresent invention.

Typically, people or users have different preferences on servicechannels. For example, men prefer sports channels, women prefer dramaand movie channels, and students prefer music and game channels.Accordingly, it can be considered to register favorite service channelsin accordance with the user preference in the form of channel list.

Referring to FIG. 10, if broadcast data are received (S711), thecontroller 100 determines whether a PID contained in the broadcast datais identical with the PID of the ongoing service channel (S713). If thereceived broadcast data have the PID of the ongoing service channel, thecontroller 100 controls the decapsulation of an IP datagram from thereceived broadcast data (S715) and extracts video and audio data fromthe IP datagram (S717). Next, the controller 100 controls the decodingof the video and audio data (S719) and outputs the decoded video andaudio data through the display unit 150 and the speaker 155 (S721),respectively. If the PID of the received broadcast data is not identicalwith the PID assigned to the ongoing service channel at step S713, thecontroller 100 determines whether the PID of the received data isidentical with one of the PIDs assigned to the standby service channels(S731). In this embodiment, the standby service channels are thefavorite service channels registered in accordance with the userpreference. The favorite service channels can be registered by the useror selected on the basis of the analysis of channel switching pattern ofthe user. Also, the number of the favorite service channel can bechanged or determined dependant on the number of the buffers 331 to 33N.

If the PID of the received broadcast data is identical with one of thePIDs assigned to the standby service channels, the controller 100determines whether the PID is of a first buffer (S733). If the PID is ofthe first buffer, the controller 100 controls the storing of thebroadcast data within the first buffer (S735). If the PID is not of thefirst buffer at step S733, the controller 100 determines whether the PIDis of a second buffer (S737). If the PID is of the second buffer, thecontroller 100 controls the storing or buffering of the broadcast withina second buffer (S739). That is, the controller 100 controls thebroadcast demodulator 120 to output the broadcast data having the PIDsof the ongoing and standby service channels and controls the storageunit 130 to buffer the broadcast data output from the broadcastdemodulator within corresponding buffers distinguished by the PIDs. Forexample, assuming that the ongoing service channel is CH4 and thestandby service channels, i.e. favorite channels, are CH2 and CH6 as inFIG. 6E, the controller 100 plays the broadcast data received throughthe ongoing service channel CH4 (S733 to S735) while buffering thebroadcast data received through the standby service channels CH2 and CH6(S737 to S739).

If a channel switching signal is input through key input unit 170, thecontroller 100 performs a channel switching procedure (S550, FIG. 7) andthen returns to the broadcast playback procedure for playing thebroadcast data of the new ongoing service channel (S540).

FIG. 11 is a flowchart illustrating a channel switching procedure of afast channel switching method according to the exemplary embodiment ofthe present invention shown in FIG. 10.

Referring to FIG. 11, if a channel switching signal is detected, thecontroller 100 determines whether a switching target service channelindicated by the channel switching signal is one of the standby servicechannels, i.e. preset favorite service channels (S751). If the switchingtarget service channel is one of the standby service channels, thecontroller 100 controls the start of playing the broadcast data bufferedwithin the buffer assigned for the switching target service channel(S753) and sets the switching target service channel as a new ongoingservice channel (S755).

After switching to the new ongoing service channel, the controller 100determines whether the previous ongoing service channel is one of thefavorite service channels (S757). If the previous ongoing servicechannel is one of the favorite service channels, the controller 100 setsthe previous ongoing channel as one of the standby service channels(S759), or, the controller 100 withdraws the PID of the previous ongoingservice channel (S761). That is, after setting the PID of the newongoing service channel, the controller 100 sets the PIDs of the standbyservice channels. Here, the previous ongoing service channel can be oneof the standby service channels or not according to whether the previousongoing service channel is one of the favorite service channels.

If the selected service channel is not one of the standby servicechannels at step S751, the controller 100 set the PID of the selectedservice channel for the ongoing service channel and carries out stepS757. In this case, since there is no buffered broadcast data of the newongoing service channel, the broadcast playback may be delayed until thenext data burst is received.

Referring to the example of FIG. 6E, if a channel switching signal isinput for selecting the standby service channel CH2 (or CH6), whileplaying the broadcast data of the ongoing service channel CH4 andbuffering the broadcast data of the standby service channels CH2 andCH6, the controller 100 regards the service channel CH2 indicated by thechannel switching signal as a target service channel at step S751,provides controls such that the broadcast data buffered for the standbyservice channel CH2 are read out at step S753, and sets the targetservice channel CH2 as the new ongoing service channel at step S755.Since the previous ongoing service channel CH4 is one of the favoriteservice channels, the controller 100 sets the previous ongoing servicechannel CH4 as one of the new standby service channels. On the otherhand, if the channel switching signal indicates the service channel CH3as a target service channel, the controller 100 sets the service channelCH3 as a new ongoing service channel, and sets the previous ongoingservice channel CH4 as a standby service channel. In a case that achannel switching signal indicates a non-standby service channel (forexample, CH1) as a target signal while playing the broadcast data of theongoing service channel (for example, CH3) which is also not registeredas one of the favorite service channels, the controller 100 sets thetarget service channel CH1 as a new ongoing service channel andwithdraws the PID of the previous ongoing service channel CH3. At thistime, the favorite service channels CH2, CH4, and CH6 are maintained asthe standby service channels.

A channel switching operation, when a channel switching signal is inputwhile buffering the broadcast data of the favorite service channels, isdescribed with reference to FIGS. 1 to 4. In this embodiment, thechannel switching is performed in consideration of 4 differentsituations. First situation is a case in which both the ongoing servicechannel and the switching target service channel are favorite servicechannels. Second situation is a case in which the ongoing servicechannel is a non-favorite service channel and the switching targetservice channel is a favorite service channel. Third situation is a casein which the ongoing service channel is a favorite service channel andthe switching target service channel is a non-favorite service channel.And, fourth situation is a case in which both the ongoing and switchingtarget service channels are non-favorite service channels.

In the case of the first situation, if it is determined that both theongoing service channel and the switching target service channel arefavorite service channels, the controller 100 controls the secondselector 340 of the storage unit 130 to read out the broadcast databuffered within the buffer set with the PID of the switching targetservice channel, i.e. a new ongoing service channel. Next, thecontroller 100 controls the broadcast demodulator 120 to maintain thePIDs of the favorite service channels set for the PID filter 230 suchthat the first selector 320 writes the broadcast data of the favoriteservice channels within the buffers 331 to 33N assigned the PIDs of thefavorite service channels. Accordingly, the output of the bufferassigned the PID of the new ongoing service channel is delivered to thebroadcast decoder 140. The broadcast decoder 140 decodes the broadcastdata from the buffer of the new ongoing service channel and outputs thedecoded video and audio data through the display unit 150 and speaker155. If the next data burst of the new ongoing service channel isreceived while playing the buffered broadcast data, the storage unit 130stores the broadcast data within the corresponding buffer assigned thePID of the ongoing service channel so as to be output following thebuffered broadcast data. At this time, the second selector 340 reads outthe broadcast data store in the buffer set with the PID of the ongoingservice channel. Accordingly, the broadcast decoder 140 decodes thebuffered broadcast data and the broadcast data received at the nextburst time of the new ongoing service channel without delay of thebroadcast data stream, resulting in seamless channel switching.

In the case of the second situation, if it is determined that theongoing service channel is a non-favorite service channel and theswitching target service channel is a favorite service channel, thecontroller 100 controls the second selector 340 of the storage unit 130to read out the broadcast data buffered within the buffer set with thePID of the switching target service channel, i.e. a new ongoing servicechannel. next the controller 100 controls the broadcast data of thebroadcast demodulator 120 to maintain the PIDs of the favorite servicechannels set for the PID filter 230 such that the first selector 320writes the broadcast data of the favorite service channels within thebuffers 331 to 33N assigned the PIDs of the favorite service channels.Accordingly, the output of the buffer assigned the PID of the newongoing service channel is delivered to the broadcast decoder 140. Thebroadcast decoder 140 decodes the broadcast data from the buffer of thenew ongoing service channel and outputs the decoded video and audio datathrough the display unit 150 and speaker 155. If the next data burst ofthe new ongoing service channel is received while playing the bufferedbroadcast data, the storage unit 130 stores the broadcast data withinthe corresponding buffer assigned the PID of the ongoing service channelso as to be output following the buffered broadcast data. Since theprevious ongoing service channel is non-favorite service channel, thePID of the previous ongoing service channel is withdrawn from the PIDfilter 230 and storage unit 130, resulting in no more buffering. In thiscase, the broadcast decoder 140 also decodes the buffered broadcast dataand the broadcast data received at the next burst time of the newongoing service channel without delay of the broadcast data stream.

In the case of third situation, if it is determined that the ongoingservice channel is a favorite service channel and the switching targetservice channel is a non-favorite service channel, the controller 100controls the second selector 340 to set a buffer for buffering thebroadcast data of the switching target service channel, i.e. a newongoing service channel. Since there is no buffered broadcast data forthe switching target service channel, data streams played on the display150 and output through the speaker 155 may be interrupted. After settingthe buffer, the controller 100 controls the broadcast demodulator 120 tomaintain the PIDs of the favorite service channels set for the PIDfilter 230 and adds the PID of the new ongoing service channel to thePID filter 230 such that the first selector 320 writes the broadcastdata of the favorite service channels and the new ongoing servicechannel within the corresponding buffers assigned the PIDs of thefavorite service channels and the new ongoing service channel. In thiscase, playback of the broadcast data may be delayed until receiving thenext data burst of the new ongoing service channel.

In the case of the fourth situation, if it is determined that both theongoing and switching target service channels are non-favorite servicechannels, the controller 100 controls the second selector 340 of thestorage unit 130 to set a buffer for buffering the broadcast data of theswitching target service channel, i.e. a new ongoing service channel.Since there is no buffered broadcast data for the switching targetservice channel, data streams played on the display 150 and outputthrough the speaker may be interrupted. After setting the buffer, thecontroller 100 controls the broadcast demodulator 120 to maintain thePIDs of the favorite service channels set for the PID filter 230 andadds the PID of the new ongoing service channel to the PID filter 230such that the first selector 320 write the broadcast data of thefavorite service channels and the new ongoing service channel within thecorresponding buffers assigned the PIDs of the favorite service channelsand the new ongoing service channel and withdraws the PID of theprevious ongoing service channel from the PID filter 230. The controller100 also controls the first selector 320 of the storage unit 130 towrite the broadcast data received through the favorite service channelsand the new ongoing service channel into the corresponding buffers. Inthis case, playback of the broadcast data may be delayed until receivingthe next data burst of the new ongoing service channel.

In the cases of the third and fourth situations, channel switching delaymay occur. In this embodiment, one of the buffers 331 to 33N can bereserved for storing specific multimedia data which is output when thenon-favorite service channel is selected as the switching target servicechannel. The buffer storing the multimedia data is selected by thesecond selector 340 when a non-favorite service channel is selected asthe switching target service channel such that the multimedia data areplayed until the next burst data of the new ongoing service channel arereceived, resulting in avoidance of data stream breakage. The multimediadata can be stored in the separate memory 160 rather than a buffer ofthe storage unit 130. The size of the multimedia data is determined inconsideration of the channel switching delay.

In this embodiment, the favorite channel-based fast channel switchingmethod creates favorite channel list consisting of channels selected bythe user or in accordance with a preference analysis, buffers thebroadcast data while playing the broadcast data of an ongoing servicechannel, and plays, if one of the favorite service channels is selectedas a new ongoing service channel, the buffered broadcast data, withoutchannel switching delay.

As described above, the standby service channels represent the neighborservice channels in the first embodiment and the favorite servicechannels in the second embodiment. The broadcast data of the standbyservice channels are buffered while the broadcast data received throughthe ongoing channel are played. If a channel switching is detected suchthat one of the standby service channels is selected, the bufferedbroadcast data of the selected standby service channel are played untilthe next data burst of the selected standby service channel.Accordingly, the channel switching is quickly performed with processingdelay and a subscriber can watch the display image with delay at thetime when the channel switching occurs. In the following embodiment, thefast channel switching method is implemented with both the neighborchannel buffering and favorite channel buffering techniques. Channelswitching can be performed with the navigation keys, i.e. the up anddown keys, or with the number key or memory keys matched with specificchannels. In the case using the navigation keys, the service channelscan be sequentially selected when the navigation key is pressed, wherebyit is advantageous to use the neighbor channel-based standby servicechannel designation scheme. In the case using the number keys, however,the favorite channel-based standby service channel designation scheme isadvantageous since the channel is randomly selected. Accordingly, byadopting both the neighbor channel-based standby service channeldesignation scheme and the favorite channel-based standby servicechannel designation for the fast switching method, the reliability ofthe fast channel switching method can be improved.

The main procedures of the fast channel switching method according tothe third embodiment of the present invention is identical with that ofFIG. 7 except for the playback procedure (S540) and the channelswitching procedure (S550).

FIG. 12 is a flowchart illustrating a broadcast playback procedure of afast channel switching method according to this third exemplaryembodiment of the present invention. In this embodiment, broadcast dataof the neighbor service channels and the favorite service channels arebuffered.

Referring to FIG. 12, if broadcast data are received (S811), thecontroller 100 determines whether a PID contained in the broadcast datais identical with the PID of the ongoing service channel (S813). If thereceived broadcast data have the PID of the ongoing service channel, thecontroller 100 controls the decapsulation of an IP datagram from thereceived broadcast data (S815) and extracts video and audio data fromthe IP datagram (S817). Next, the controller 100 controls the decodingof the video and audio data (S819) and outputting of the decoded videoand audio data through the display unit 150 and the speaker 155 (S821),respectively. If the PID of the received broadcast data is not identicalwith the PID assigned to the ongoing service channel at step S813, thecontroller 100 determines whether the PID of the received data isidentical with one of the PIDs assigned to one of the standby servicechannels (S831). If the PID of the received data is identical with oneof the PIDs assigned to one of the standby service channels, thecontroller 100 determines whether the PID is of one of the neighborservice channels (S833). If the PID is of one of the neighbor servicechannels, the controller 100 buffers the broadcast data within thebuffer of the corresponding neighbor service channel (S835). At thistime, the broadcast data can be buffered in a manner identical withsteps 633 to 637 of FIG. 8. If the PID is not of one of the neighborservice channels, the controller 100 buffers the broadcast data withinthe buffer of the corresponding favorite service channel (S837).

FIG. 13 is a flowchart illustrating a channel switching procedure of afast channel switching method according to this third exemplaryembodiment of the present invention.

Referring to FIG. 13, when a channel switching signal is detected, thecontroller 100 determines whether a switching target service channelindicated by the channel switching signal is one of the standby servicechannels (S851). If the switching target service channel is one of thestandby service channels, the controller 100 controls the output of thebroadcast data buffered within the buffer assigned for the switchingtarget standby service channel (S853) and determines whether theswitching target service channel is one of the neighbor service channels(S855). If the switching target service channel is one of the neighborservice channels, the controller 100 resets PIDs of the PID filter 230of the broadcast demodulator 120 and the buffers of the storage unit 130for new neighbor service channels (S857). The PID reset can be performedin a manner identical with steps 653 to 661 of FIG. 9. If the switchingtarget service channel is not one of the neighbor service channels, thecontroller 100 resets PIDs of the PID filter 230 of the broadcastdemodulator 120, particularly the PID of the previous ongoing servicechannel, and the buffers 331 to 33N of the storage unit 130 for thefavorite service channels (S859). At this time, the PID reset can beperformed in a manner identical with steps S757 to S761 of FIG. 11. Inthe meantime, if the switching target service channel is not one of thestandby service channels, the controller 100 sets the switching targetservice channel as a new ongoing service channel (S861) and then resetsPIDs of the PID filter 230 of the broadcast demodulator 120 and thebuffers 331 to 33N of the storage unit 130 for the favorite servicechannels (S859).

The neighbor service channels and the favorite service channels may beoverlapped. In this case, it is preferred that the controller 100controls the broadcast data of the overlapped service channel within onebuffer of the storage unit 130.

In order to prevent the same broadcast data from being buffered withintwo buffers, standby service channel designation priorities can beconsidered. That is, if the favorite service channel has a higherdesignation priority, the controller 100 checks whether a neighborservice channel is registered as a favorite service channel. If theneighbor service channel is registered as a favorite service channel,the controller 100 manages the service channel as the favorite servicechannel rather than the neighbor service channel. On the other hand, ifthe neighbor service channel has a higher designation priority, thecontroller 100 manages the overlapped service channel as the neighborservice channel rather than the favorite service channel. In thefollowing embodiment, it is assumed that the favorite service channelhas a higher designation priority.

FIG. 14 is a flowchart illustrating a standby service channel settingprocedure of the fast channel switching method according to an exemplaryembodiment of the present invention. If it is determined that aswitching target service channel is one of the standby service channels,the controller 100 determines whether the switching target servicechannel is one of the neighbor service channels. If the switching targetservice channel is one of the neighbor service channels, the controller100 also checks the switching target service channel is one of thefavorite service channels. If the switching target service channelbelongs to both the neighbor and favorite service channels, thecontroller 100 manages the switching target service channel as afavorite service channel so as to maintain the PID and buffer of thefavorite service channel corresponding to the switching target servicechannel. However, if the switching target service channel belongs toonly the neighbor service channels, the controller 100 resets the PIDfilter and the buffers.

Referring to FIG. 14, if a switching control signal is input, thecontroller 100 determines whether the switching target service channelindicated by the switching control signal is the upper neighbor servicechannel (S871). If the switching target service channel is the upperneighbor service channel, the controller 100 determines whether theongoing service channel is one of the favorite service channels (S873).If the ongoing service channel is one of the favorite service channels,the controller 100 maintains the PID and buffer of the ongoing servicechannels as a favorite service channel, or, the controller 100 withdrawsthe PID of the previous ongoing service channel from the PID filter 230and disables the buffer of the previous ongoing service channel in thestorage unit 130 (S875). Next, the controller 100 determines whether theupper neighbor service channel of the switched-to target service channelis one of the favorite service channels (S877). If the upper neighborservice channel of the switched-to target service channel is one of thefavorite service channels, the controller 100 maintains the PID andbuffer of the upper neighbor service channel. Otherwise, controller 100adds the PID of the upper neighbor service channel to the PID filter 230and creates a buffer in the storage unit 130 for the upper neighborservice channel (S879).

If the switched-to target service channel is not the upper neighborservice channel at step S871, the controller 100 regards the switchingtarget service channel as the lower neighbor service channel anddetermines whether the previous upper neighbor service channel is one ofthe favorite service channels (S881). If the previous upper neighborservice channel is one of the favorite service channels, the controller100 maintains the PID and buffer of the previous upper neighbor servicechannel. Otherwise, the controller 100 disables the PID of the previousupper neighbor service channel in the PID filter 230 and disables thebuffer of the previous upper neighbor service channel in the storageunit 130 (S883). Next, the controller 100 determines whether the lowerneighbor service channel of the switching target service channel is oneof the favorite service channels (S885). If the lower neighbor servicechannel of the switching target service channel is one of the favoriteservice channels, the controller 100 maintains the PID and buffer of thelower neighbor service channel. Otherwise, the controller 100 adds thePID of the lower neighbor service channel to the PID filter 230 andcreates a buffer for the lower neighbor service channel (S887).

A service channel buffering mechanism is described hereinafter withreference to FIG. 6A. In the embodiment, the broadcast data of theongoing service channel and the service channels CH1, CH2, and CH4 toCH6 are buffered. Accordingly, when the ongoing service channel isswitched to another channel, the broadcast data buffered for the newongoing service channel are read out to be played, thereby reducingchannel switching delay. The buffering operation can be executed in asequential order or a directional order.

The sequential order-based buffering mechanism is described withreference to FIG. 6A. In FIG. 6A, the ongoing service channel is CH3, anumber of the standby service channels is 2, and the buffering isperformed in an ascending order.

The controller 100 sets up the broadcast demodulator 120 with the PIDsof the service channels CH3 to CH5 and controls the second selector 340to read out the broadcast data stored in the buffer of the storage unit130 assigned for the CH3. In this case, PID filter 230 of the broadcastdemodulator 120 filters the broadcast data of CH3, CH4, and CH5. Thecontroller 100 controls the first selector 320 to switch the broadcastdata output from the broadcast demodulator 120 to the buffers such thatthe broadcast data of CH3, CH4, and CH5 are buffered in the buffersassigned for channels CH3, CH4, and CH5. Next, the controller 100 resetsthe PID filter 230 of the broadcast demodulator 120 with the PIDs of theCH3, CH6, and CH1 for buffering the broadcast data of the correspondingservice channels at their burst times. The number of the servicechannels to be buffered can be changed by the user configuration. Also,the buffering can be performed in a descending order. In this case, thebuffering is performed in an order of CH2, CH1, and CH6.

The directional order-based buffering mechanism is described withreference to FIG. 6A. In FIG. 6A, the ongoing service channel is CH3. Inthe broadcast mode, the controller 100 sets up the PID filter 230 of thebroadcast demodulator 120 with the PIDs of the ongoing channels CH3 andthe neighbor service channels CH4 and CH2 and controls the secondselector 340 to read out the broadcast data stored in the bufferassigned for the ongoing service channel CH3 to the broadcast decoder140. At this time, the PID filter 230 filters the broadcast data havingthe PIDs of the service channels CH2, CH3, and CH4. The controller 100controls the first selector 320 to switch the broadcast data output fromthe broadcast demodulator 120 to the buffers such that the broadcastdata of the CH2, CH3, and CH4 are buffered in the buffers assigned forchannels CH2, CH3, and CH4. Next, the controller 100 resets the PIDfilter 230 of the broadcast demodulator 120 with the PIDs of the CH3,CH1, and CH5 for buffering the broadcast data of the correspondingservice channels at their burst times. The number of the servicechannels can be changed by the user configuration.

In the case that the buffering mechanism operates with the favoriteservice channels, one of the standby service channel selection can beexcluded. That is, if the channel buffering is configured with asequential order buffering, an ongoing service channel CH1, a favoriteservice channel CH5, and one (1) standby service channel, the standbyservice channel can be selected in association with the ongoing servicechannel, favorite service channel, and sequential ordering. Accordingly,the PID filter 230 is set with the PIDs of CH3, CH4, and CH5 in thefirst time frame, set with PIDs of CH3, CH5, and CH6 in the second timeframe, and set with PIDs of CH3, CH6, and CH1 in the third time frame.This can be adopted with the directional buffering mechanism. In thecase that a favorite service channel is set as the standby servicechannel, the controller 100 sets the PID of the service channel next tothe favorite service channel as the standby service channel.

FIG. 15 is a flowchart illustrating a broadcast playback procedure of afast channel switching method according to an exemplary embodiment ofthe present invention.

Referring to FIG. 15, if broadcast data are received, the controller 100detects the broadcast data (S1611), the controller 100 determineswhether a PID of the received broadcast data is identical with the PIDof the ongoing service channel (S1613). If the PID of the receivedbroadcast data is identical with the PID of the ongoing service channel,the controller 100 controls the decapsulation of an IP datagram from thereceived broadcast data (S1615) and extraction of video and audio datafrom the IP datagram (S1617). Next, the controller 100 controls thedecoding of the video and audio data (S1619) and outputting of thedecoded video and audio data through the display unit 150 and thespeaker 155 (S1621).

If the PID of the received broadcast data is not identical with the PIDof the ongoing service channel at step S1613, the controller 100determines whether the PID of the received broadcast data is identicalwith one of the PIDs of the standby service channels (S1631). If the PIDof the received data is identical with one of the PIDs of the standbyservice channels, the controller 100 stores the broadcast data in thebuffer assigned for the corresponding standby service channel (1633) andresets the PID filter and buffers with the PIDs of the service channelsto be buffered in the next time frame (S1635).

If the PID of the received data is not identical with one of the PIDs ofthe standby service channels, the controller 100 continues monitoringthe broadcast data.

The PID reset procedure of step S1635 can be performed in accordancewith the buffering mechanism determined at step S530 of FIG. 7, which isdepicted in FIGS. 16 and 17 in detail.

FIG. 16 is a flowchart illustrating a standby channel bufferingprocedure of FIG. 15 when no favorite service channels are set.

Referring to FIG. 16, the controller 100 checks a buffering mode of thebroadcast receiver (S1711). If the broadcast receiver operates in asequential order-buffering mode, the controller 100 determines theservice channel to be buffered at a next burst time, sets the broadcastdemodulator 120 and the storage unit 130 with the PID of the nextservice channel to be buffered (S1713), and then enables the bufferassigned the PID of the next service channel (S1715). In the sequentialorder-buffering mode, the channel buffering can be performed in anascending channel number order or a descending channel number order.Also, the number of the channels to be buffered in a frame time can bechanged. Accordingly, the controller 100 determines the PIDs of theservice channels to be buffered in consideration of the number of thestandby service channels and the buffering mode.

Assuming that the number of the standby service channel is 2, thecurrent-buffering service channel is CH2, and the buffering mode is adescending channel number order mode in the example of FIG. 6A in whicha time frame consists of 6 service channels CH1 to CH 6 including anongoing service channel CH3, the controller 100 sets the CH6 as thetarget-buffering service channel having the low channel number as muchas 2. If the current-buffering service channel is CH6, thetarget-buffering service channel becomes CH4.

If the broadcast receiver is set up with a directional order-bufferingmode, the controller 100 determines whether the current-bufferingservice channel has a higher or lower channel number than the ongoingservice channel (S1721). If the current-buffering service channel has ahigher channel number than the ongoing service channel, the controller100 determines whether the channel number of the current-bufferingservice channel is the highest channel number (S1723). If the channelnumber of the current-buffering service channel is not the highestchannel number, the controller 100 selects the service channel having anext channel number as the target-buffering service channel (S1725). Onthe other hand, if the channel number of the current-buffering servicechannel is the highest channel number, the controller 100 selectshighest numbered service channel of the ongoing service channel as thetarget-buffering service channel (S1727). After selecting thetarget-buffering service channel, the controller 100 enables the bufferassigned the PID of the target-buffering service channel (S1729). If thecurrent-buffering service channel has a lower channel number than theongoing service channel at step S1721, the controller 100 determineswhether the channel number of the current-buffering service channel isthe lowest channel number (S1731). If the channel number of thecurrent-buffering service channel is not the lowest channel number, thecontroller 100 selects the service channel having a next lower channelnumber as the target-buffering service channel (S1737). On the otherhand, if the channel number of the current-buffering service channel isthe lowest channel number, the controller 100 sets the lowest numberedservice channel of the ongoing service channel as the target-bufferingservice channel (S1735). After selecting the target-buffering servicechannel, the controller 100 enables the buffer assigned the PID of thetarget-buffering service channel (S1737).

Assuming that the buffering mode is the directional buffering mode, thecurrent-buffering service channel is CH5, upper service channels are CH4to CH6 (or CH4 and CH5), and lower service channels are CH2 and CH1 (orCH2, CH1, and CH6) in the example of FIG. 6A in which a time frameconsists of 6 service channels CH1 to CH6 including an ongoing servicechannel CH3, the controller 100 sets the service channel CH6, which isthe service channel having the next higher channel number, as thetarget-buffering service channel. If the current-buffering servicechannel is CH2, the target-buffering service channel becomes CH1. In thecase that the current-buffering service channel is CH1, the controller100 sets the next higher numbered service channel CH2 as thetarget-buffering service channel.

FIG. 17 is a flowchart illustrating a standby channel bufferingprocedure of FIG. 15 when favorite channels are set.

Typically, people or users have different preferences regarding servicechannels. For example, men prefer sports channels, women prefer dramaand movie channels, and students prefer music and game channels.Accordingly, it can be considered to register favorite service channelsin accordance with the user preference in the form of favorite channellist.

Referring to FIG. 17, the controller 100 checks a buffering mode of thebroadcast receiver (S1751). If the broadcast receiver 100 operates in asequential order-buffering mode, the controller 100 determines whether anext ordered service channel is a favorite service channel (S1753). Ifthe next ordered service channel is not a favorite service channel, thecontroller 100 performs the service channel buffering in the same mannerof steps S1713 to S1715 of FIG. 16 (S1755). In contrast, if a nextordered service channel is a favorite service, the controller 100 skipsthe service channel (S1757) and repeats step S1753.

Concerning the example of FIG. 6A in which a time frame consists of 6service channels CH1 to CH6 including an ongoing service channel CH3, afavorite service channel CH5, and a current buffering service channelCH4, and the target buffering channel number increases by 1 in anascending order, the controller 100 detects that the next servicechannel CH5 is a favorite service channel at step S1753 so skips theservice channel CH5 and then repeats the favorite channel checkingprocess with the next service channel CH6 at step 1753.

If the broadcast receiver 100 operates in a directional order-bufferingmode, the controller 100 determines whether a next ordered servicechannel is a favorite service channel (S1761). If the next orderedservice channel is not a favorite service channel, the controller 100performs the service channel buffering in the same manner of steps S1721to S1737 of FIG. 16 (S1763). In contrast, if a next ordered servicechannel is a favorite service channel, the controller 100 skips theservice channel (S1765) and repeats step S1761.

Concerning the example of FIG. 6A in which a time frame consists of 6service channels CH1 to CH6 including an ongoing service channel CH3, afavorite service channel CH5, and a current buffering service channelCH4, and the target buffering channel number increases by 1 in aascending order, the controller 100 detects that the next servicechannel CH5 is a favorite service channel at step S1761 so as to skipsthe service channel CH5 at step S1765 and then repeats the favoritechannel checking process with the next service channel CH6 at sep S1761.

If a channel switching command is detected while operating in suchbuffering mode, the controller 100 detects the channel switching commandat step S1623 of FIG. 15 and performs the channel switching procedureS550 of FIG. 7. The controller 100 can thus perform seamless channelswitching by playing, when the ongoing service channel is switched toanother service channel, the broadcast data buffered in the bufferassigned the PID of the new ongoing service channel. If a key input forending the broadcast playback mode while playing the broadcast data ofthe ongoing service channel is detected, the controller 100 ends thebroadcast playback mode.

In this embodiment, the broadcast data of all service channels arebuffered while the broadcast data of the ongoing service channel isplayed, whereby the channel switching to another channel can be quicklyperformed without displaying a blank or black screen between the videoscreens of the old and new ongoing service channels by playing thebuffered broadcast data of the new ongoing service channel.

The controller 100 controls the buffering of the broadcast data of allthe service channels while playing the broadcast data of the ongoingservice channel as described with reference to FIG. 15 at step S540 ofFIG. 7. The buffered data are used for quick and seamless channelswitching. At step S540, if a channel selection command input throughthe key input unit 170 (using channel up/down key or number keys) isdetected, the controller 100 performs the channel switching procedure ofstep S550 and then enters the broadcast playback procedure S540 forplaying the broadcast data of the new ongoing service channel.

FIG. 18 is a flowchart illustrating a channel switching procedure offast channel switching method according to another exemplary embodimentof the present invention.

Referring to FIG. 18, if a channel selection command is detected, thecontroller 100 checks the selected service channel and registers theselected service channel as the ongoing service channel (S1811). Next,the controller 100 controls the distribution of the broadcast databuffered in the buffer assigned the PID of the new ongoing servicechannel that are read out to be played (S1813). That is, the controller100 controls the second selector to read out the broadcast data bufferedfor the new ongoing service channel to the broadcast decoder 140 thatdecodes the broadcast data of the new ongoing service channel withoutdelay of the data stream. Next, the controller 100 resets the PID filterof the broadcast demodulator 120 and the buffers of the storage unit 130with new PIDs selected on the basis of the standby service channelconfiguration scheme (S1815), enters the broadcast playback mode at stepS540 of FIG. 7. At this time, the controller 100 enables the buffer ofthe selected service channel as the ongoing service channel buffer suchthat the broadcast data buffered in the buffer assigned the PID of thenew ongoing service channel is played until its next data burst isreceived. After the channel switching is completed, the controller 10controls the broadcast receiver to enter the broadcast playback mode(S540) of FIG. 7.

Since the broadcast data buffered for the newly selected service channelis played before the next data burst of the service channel beingreceived, no empty frame is displayed during the channel switchingprocess, resulting in seamless channel switching.

A channel switching operation, when a channel selecting command isdetected while buffering the broadcast data of the service channels, isdescribed with reference to FIGS. 1 to 4. If a channel selecting commandis detected, the controller 100 sets up the broadcast demodulator 120with the PID of the service channel indicated by the channel selectingcommand as the ongoing service channel PID and controls the secondselector 340 of the storage unit 130 to read out the broadcast databuffered in the buffer assigned the PID of the selected service channelto the broadcast decoder 140. Thus, the broadcast receiver can play thebroadcast data of the old and new ongoing service channel without adecoding gap therebetween.

The broadcast data played during the switching process are the broadcastdata buffered in the buffer assigned the PID of the newly selectedservice channel. Since the data burst of each service channel isreceived during a 1 to 4 second cycle, the buffer size is preferablydetermined in consideration of the data burst reception cycle. While thebuffered broadcast data are played, the controller 100 updates theongoing and standby service channels and resets the broadcastdemultiplexer 120 and the storage unit 130 with the updated ongoing andstandby service channels.

Concerning the example of FIG. 6A in which a time frame consists of 6service channels CH1 to CH6 including an ongoing service channel CH3,the controller 100 controls such that the broadcast data buffered in thebuffer assigned the PID of the CH3 is read out to be played. If achannel selection command indicating the service channel CH5 is detectedwhile playing the broadcast data of the service channel CH3, thecontroller 100 resets the ongoing service channel PID of the broadcastdemodulator 120 to the PID of the service channel CH5 (S1811). At thistime, the controller 100 checks whether the CH3 is a favorite servicechannel. If the PID is a favorite service channel, the controller 100controls the broadcast demodulator 120 to maintain the PID of the CH3,and otherwise, the controller 100 controls the deletion of the PID.Next, the controller 100 controls the second selector 340 of the storageunit 130 to read out the broadcast data buffered in the buffer assignedthe PID of the CH5 to the broadcast decoder 140 (S1813). The broadcastdecoder 140 starts decoding the broadcast of the service channel CH5without recognition of a channel switch such that the decoded broadcastdata are output through the display 150 and speaker 155 in a seamlessmanner.

During the channel switching process, the controller 100 updates thePIDs of the ongoing and standby service channels to be buffered. In thecase of using the ascending-sequential order buffering in which thechannel number increases by 1, the controller 100 sets the broadcastdemodulator 120 with the PID of the service channel CH6 and controls thefirst selector 320 to store the broadcast data of the service channelCH6 in the buffer assigned the PID of the CH6 (S1815). In the case ofusing the directional-order buffering, the controller 100 checks thebuffering order direction (for example, upward direction in an order ofCH6, CH1, and CH2; or downward direction in an order of CH4 and CH3),and determines the next service channel CH6 or CH4 to be buffered on thebasis of the buffering order direction. Next, the controller 100 setsthe broadcast demodulator 120 with the PID of the CH6 or CH4 andcontrols the first selector 320 to store the broadcast data of the CH6or CH4 in the buffer assigned the PID of the CH6 or CH4. Since all theservice channels are buffered in this embodiment, the PID reset processcan be omitted. In this case, the buffering operation (the sequentialordered buffering or directional ordered buffering operation) isexecuted without PID update.

Although the fast channel switching method and apparatus of FIGS. 1 to14 are described with regard to a DVB-H receiver, the present inventionis not limited thereto. For example, the fast channel switching methodand apparatus can be adopted to other digital broadcast receivers.

FIG. 19 is a block diagram illustrating a digital broadcast receiveradopting a fast channel switching apparatus and method according to anexemplary embodiment of the present invention.

Referring to FIG. 19, the digital broadcast receiver includes acontroller, 900, a tuner 910, a broadcast demodulator 920, ademultiplexer 930, a storage unit 940, a broadcast decoder 950, adisplay unit 960, a speaker 965, a memory unit 970, and a key input unit980.

The controller 900 controls general operations of the digital broadcastreceiver. The key input unit 980 generates key signals and transfers thekey signals to the controller 900. The memory unit 970 includes aprogram memory for storing application programs for controlling theoperation of the digital broadcast receiver and a data memory forstoring application data generated while executing the applicationprograms. Particularly, program memory of the memory unit 970 can storethe application program for buffering the broadcast service channels.The controller 900 also controls the channel switching procedureaccording to an embodiment of the present invention. That is, thecontroller 900 controls playback, recording, and channel selection andswitching operations of the digital broadcast receiver.

The tuner 910 sets a physical channel, i.e. the frequency, of theservice channel selected by the user, and receives broadcast signalsthrough the physical channel. The broadcast demodulator 920 demodulatesthe broadcast signal received through the tuner 910. The broadcastdemodulator 920 demodulates the broadcast data of multiple servicechannels. The demultiplexer 930 performs demultiplexing on the broadcastdata having a PID of a selected service channel. The storage unit 940buffers the broadcast data output from the demultiplexer 930 under thecontrol of the controller 900. The broadcast decoder 950 decodes thebroadcast data read out from the storage unit 940. The broadcast datacan be implemented with video and audio decoders such that video andaudio data decoded from the broadcast data are output through thedisplay unit 960 and the speaker 965.

As depicted in FIG. 19, the DVB-T and DMB differ from DVB-H in sometechnical features. Unlike the DVB-H, the DVB-T and DMB do not user IPinformation, and the broadcast demodulator 920 of the DVB-H or DMBreceiver do not perform PID filtering. Accordingly, the demultiplexer930 of the digital broadcast receiver in FIG. 19 should perform PIDfiltering, and the storage unit 940 buffers the broadcast data of theongoing and standby service channels output from the demultiplexer 930.The DVB-T and DMB do not user the time slicing scheme and thus thedigital broadcast receiver checks the ongoing and standby servicechannel using the service channel identifier of the broadcast data. Inthe case of DVB-T and DMB that do not use the time slicing scheme, thedigital broadcast receiver always checks the ongoing service channelsuch that the standby service channels are checked whenever the ongoingservice channel is updated in a predetermined time interval. In thiscase, the standby service channels are updated in a predetermined timeinterval (for example, 1 second, 2 seconds, 3 seconds, etc.).

The demultiplexer 930 selects the ongoing and standby service channelsand demodulates the broadcast data per the service channel. Thedemultiplexing operation of the demultiplexer 930 of the DVB-T receiveris described hereinafter.

The broadcast data are received in the form of MPEG2-TS packet streams.The TS packets can be classified into a video packet and audio packet.The video and audio packets are multiplexed to be transmitted. Eachpacket includes a packet header and a payload containing at least one ofsupplementary information, a Packet Elementary Stream header (PES), andaudio or video data. The TS packet has a length of 188 bytes consistingof 4-byte header and 184-byte payload. Table 1 shows parameterscontaining in the packet header.

TABLE 1 Parameter Description Bits Sync byte Synchronization byte, 0X478 Transport error Error occurrence in current packet: 1 1 indicatorPayload start Current packet starts PES: 1 1 indicator Transportpriority Using in decoder 1 PID Identifier for distinguishing packettype 13 Scrambling control Set scrambling mode 2 Adaptation field 01: nosupplementary information/only 2 control payload 10: only supplementaryinformation/no payload 11: supplementary information & payload 00:reserved Continuity 4 byte counter, increase by 1 for same PID 4 counter

A packet header starts a synchronization byte such that the packets canbe distinguished using the synchronization byte. The demultiplexer 930is set with the PIDs of the ongoing and standby service channels by thecontroller 100. Accordingly, the demultiplexer 930 checks thesynchronization byte of the packet, analyzes the rest of the packetheader, and processes the broadcast data of the ongoing and standbyservice channels. That is, the demultiplexer 930 compares the PID of thereceived broadcast data with the PIDs set for the ongoing and standbyservice channels and performs demultiplexing of the broadcast datahaving the PID of the ongoing or standby service channels.

If the PID of the received broadcast data is identical with one of thePIDs set in the demultiplexer 930, the controller 100 checks theadaptation field control parameter for determining whether supplementaryinformation exists. If no supplementary information is included, i.e.the packet contains only the PES header and/or audio and video (A/V)data, the multiplexer 930 skips the supplementary information processingoperation. The packet having no supplementary information carries onlythe PES header and A/V data in the payload.

The controller 100 sets the demultiplexer 930 with the PIDs of theongoing and standby service channels such that the demultiplexer 930checks the TS packets output from the demodulator 920 and performsdemultiplexing on the TS packets having one of the PIDs. Thedemultiplexer 930 performs demultiplexing on the TS packets so as tooutput video and audio data.

The controller 100 controls the storage unit 940 to buffer the broadcastdata of the ongoing and standby service channels. At this time, thestorage unit 940 can be implemented with the configuration of FIG. 3. Inthis case, the controller 100 controls the first selector 320 to writethe broadcast data of the ongoing and standby service channels outputfrom the demultiplexer 930 into the corresponding buffers 331 to 33N,and controls the second selector 340 to read out the broadcast data ofthe service channel from the storage unit 940 to the broadcast decoder950. The demultiplexer 930 outputs demultiplexed video and audio datafor corresponding service channels. Accordingly, it is preferred toconfigure the storage unit 940 to buffer the video and audio data of therespective service channels into the buffers 331 to 33N separately. Thesecond selector 340 reads out the video and audio data of the ongoingservice channel to respective video and audio decoders of the broadcastdecoder 950, such that the video and audio data decoded by the video andaudio decoders are output through the display unit 960 and the speaker965. That is, the storage unit 940 buffers the broadcast data of theongoing and standby service channels and outputs only the broadcast dataof the ongoing service channel, the broadcast decoder 950 decodes thebroadcast data output from the storage unit 940 and outputs decodedvideo and audio data through the display unit 960 and the speaker 965.

The broadcast playback and channel switching operations of theabove-structured digital broadcast receiver can be performed as shown inFIG. 7. The digital broadcast receiver sets standby service channelswith the ongoing service channel, buffers the broadcast data of thestandby service channels while playing the broadcast data of the ongoingservice channel, and plays, when one of the standby service channels isselected as a switching target service channel, the buffered broadcastdata of the switching target service channel without processing delay.This procedure can be performed as shown in FIGS. 8 to 14. Since thebroadcast data received by the digital broadcast receiver of FIG. 19 arenot IP datagrams, the IP decapsulation process is not required.Accordingly, the IP decapsulation related processes should be skipped inthe broadcast playback and channel switching procedures for the digitalbroadcast receiver of FIG. 19.

The digital broadcast receiver includes digital broadcastreception-enabled mobile phones. Recently, mobile phones integrate adigital broadcast receiver.

FIG. 20 is a block diagram illustrating a mobile terminal equipped witha DVB-H receiver adopted a fast channel switching apparatus according toan exemplary embodiment, and FIG. 21 is a block diagram illustrating amobile terminal equipped with a DVB-T receiver adopting a fast channelswitching apparatus according to another exemplary embodiment of thepresent invention.

Referring to FIG. 20, the mobile phone includes a configuration of thedigital broadcast receiver of which memory unit 160, key input unit 170,display unit 150, and speaker 155 are shared by communication functionsof the mobile phone. The controller 100 controls digitalbroadcast-related operations as well as the mobile communication-relatedoperation. A radio frequency (RF) unit 190 can be implemented with afrequency converter for up-converting the baseband signal into RF signaland down-converting the RF signal into the baseband signal. A dataprocessing unit incorporating a modulation/demodulation module formodulating/demodulating the RF signal and a codec for performcoding/decoding functions can be integrated into the RF unit 190 or thecontroller 100.

The digital broadcast receiver switches off when the mobile phoneoperates in a communication mode. When the mobile phone operates in abroadcast reception mode, the communication function of the mobile phoneis disabled and the digital broadcast receiver switches on so as to playthe broadcast data received through the tuner 110.

If an incoming call is received while operating in the communicationmode, the controller 100 alerts the user of the incoming call. Anincoming call alert mode can be set by the user. The incoming call alertoperates in a normal alert mode or a mute alert mode. In the normalalert mode, the controller 100 causes the output of an incoming alertsound (for example, melody, bell, or music) and displays callerinformation on the display unit 150. In the mute alert mode, thecontroller 100 causes a motor (not shown) to vibrate the mobile phoneand display the caller information on the display unit 150. If anincoming call is received, the controller 100 displays the callerinformation together with an incoming call alert message. The incomingcall alert message can be displayed in a blinking mode to capture theuser's attention. Preferably, the incoming call alert message and thecaller information are displayed on the broadcast screen as an image.

The mobile phone allows requesting an outgoing call while operating inthe broadcast reception mode. Since the digital broadcast receiversupports the unidirectional communication, it is preferred to configurethe RF unit 190 to transmit signals even in the broadcast receptionmode. For example, while viewing a home shopping channel, the user cantransmit an order signal for buying a product promoted on the homeshopping channel. In this case, the mobile phone establishes acommunication channel to a home shopping center and transmits the ordersignal to the home shopping center. With such convergence of thebroadcast reception and communication functions, a user can easily orderfor a product in real time while viewing the home shopping channel.

In order to solve the channel switching delay problem of theconventional digital broadcast receiver, the fast channel switchingmethod and apparatus buffers broadcast data of some standby servicechannels that are likely to be selected at the next channel switchingwhile playing the broadcast of the ongoing service channel and displays,when one of the candidate services is selected, the buffered broadcastdata of the selected standby service channel, resulting in seamlesschannel switching. In the present invention, the standby servicechannels can be set in accordance with a channel selection pattern. Thestandby service channels are set with the neighbor service channels ofthe ongoing service channel for a navigation key-based channelselection, and with preset favorite service channels for a numberkey-based channel selection, resulting in reliable fast channelswitching.

Although the fast channel switching method and apparatus are implementedwith a single tuner, the present invention is not limited to the singletuner equipped broadcast receiver. For example, the present inventioncan be adopted to the broadcast receiver having more than one tuners. Inthe case of multi-tuner broadcast receiver, the controller controls tobuffer the broadcast data received through the multiple tuners for fastchannel switching as the single-tuner broadcast receiver. Themulti-tuner broadcast receiver is composed of a primary tuner forreceiving an ongoing service channel and at least one secondary tunerfor receiving at least one standby service channel. The ongoing servicechannel and standby service channels can be set by key input through thekey input unit. The tuners of the fast channel switching apparatus ofthe broadcast receiver can be tuned for different frequency channel andoperate with the favorite service channels preset for the respectivetuners. That is, the digital broadcast receiver of the present inventioncan operate in such a manner that the tuners are tuned for the receptionof favorite service channels, thereby quickly switching to anotherservice channel in response to a channel switching command by changingthe corresponding tuner. As described above, the fast channel switchingmethod and apparatus of the present invention can perform channelswitching operation without delay between broadcast streams regardlessof the number of tuners. Particularly, since the predetermined channelssuch as favorite service channels are buffered while an ongoing playbackservice channel is playing, it is possible to quickly switch the ongoingservice channel to another service channel by playing the bufferedbroadcast data of switched service channel.

Also, the fast channel switching apparatus and method of the digitalbroadcast receiver can be configured such that only the I frames or Iand P frames of corresponding service channels are buffered. In thiscase, the video data of the service channels are classified into Iframes containing entire video data, P frames generated with referenceto the variation of the video data associated with I frame, and B framesgenerated with reference to the values predicted from the I frames. Thefast channel switching method and apparatus of the digital broadcastreceiver can be configured to store only the I frame, or I and P frames.In this case, if a channel switching command is input such that a newongoing service channel is selected, the fast channel switching methodand apparatus buffers the frames following the I frame or I and P framesand plays the frames. By buffering some parts of the broadcast data, thefast channel switching method and apparatus can reduce processing loadand improve memory utilization efficiency. Although exemplaryembodiments of the present invention have been described in detailhereinabove, it should be clearly understood that many variations and/ormodifications of the basic inventive concepts herein taught which mayappear to those skilled in the present art will still fall within thespirit and scope of the present invention, as defined in the appendedclaims.

As described above, the fast channel switching method and apparatus ofthe present invention buffers broadcast data of predetermined standbyservice channels that have high probability to be selected at the nextchannel switching and plays, when one of the standby service channel isselected, the buffered broadcast data of the selected standby servicechannel without waiting for receiving the next data burst of theselected service channel, resulting in fast channel switching. Since thebuffered broadcast data of the selected service channel are played untilthe next data burst are received, no breakage of display image streamoccurs, resulting in smooth channel display switching.

What is claimed is:
 1. A mobile phone comprising: a tuner for receivingservice channels of a frequency channel; a broadcast demodulator fordemodulating the service channels and outputting an ongoing servicechannel and at least one standby service channel among the servicechannels; a storage unit for storing broadcast data of the ongoing andstandby service channels output from the broadcast demodulator intocorresponding buffers and reading out the broadcast data buffered in abuffer of the ongoing service channel; a decoder for decoding thebroadcast data read out of the storage unit and outputting video andaudio data; a controller for controlling the broadcast demodulator todemodulate the broadcast data, the storage unit to buffer broadcast dataof the ongoing and standby service channels and output the bufferedbroadcast data of the ongoing service channel; and a display fordisplaying the video data output from the decoder, wherein thecontroller controls, when the ongoing service channel is switched to oneof the standby service channels, the storage unit to read out thebuffered broadcast data of the standby service channel as a new ongoingservice channel, controls the broadcast demodulator and the storage unitif the standby service channel is an upper neighbor service channel, todelete a Program Identifier (PID) of a lower neighbor service channeland add a PID of the upper neighbor service channel of the new ongoingservice channel and controls the broadcast demodulator and the storageunit, if the standby service channel is the lower neighbor servicechannel, to delete the PID of the upper neighbor service channel of theongoing service channel and add the PID of the lower neighbor servicechannel of the new ongoing service channel.
 2. The mobile phone of claim1, wherein the controller controls the storage unit to read out, whenthe ongoing service channel is switched to one of the standby servicechannels, the buffered broadcast data of the switched standby servicechannel, and resets the broadcast demodulator and the storage withidentifier of new ongoing and standby service channels.
 3. The mobilephone of claim 2, wherein controller controls the display to display,when an incoming call is received in a broadcast mode, an incoming callalert message with caller information on the display.
 4. The mobilephone of claim 2, wherein the controller controls a radio frequency unitto transmit, when an outgoing call event occurs, the outgoing callthrough an antenna.
 5. The mobile phone of claim 1, wherein the standbyservice channels comprise channels having a higher probability forselection as an ongoing service channel during a subsequent channelswitching.
 6. A mobile phone comprising: a tuner for receiving servicechannels of a frequency channel; a broadcaster demodulator fordemodulating the service channels; a demultiplexer set with identifiersof an ongoing service channel and at least one standby service channelfor demultiplexing broadcast data of the ongoing and standby servicechannels; a storage unit for buffering the broadcast data output fromthe demultiplexer into buffers corresponding to the service channels andreading out the broadcast data buffered within the buffer of the ongoingservice channel; a broadcast decoder for decoding the broadcast dataread out of the storage unit; a controller for controlling thedemultiplexer to demultiplex the broadcast data, the storage unit tobuffer broadcast data of the ongoing and standby service channels andoutputting the buffered broadcast data of the ongoing service channel,and a radio frequency unit to process calls in a broadcast mode; adisplay for displaying the video data output from the decoder; andwherein the controller controls, when the ongoing service channel isswitched to one of the standby service channels, the storage unit toread out the buffered broadcast data of the standby service channel as anew ongoing service channel, controls the broadcast demodulator and thestorage unit if the standby service channel is a upper neighbor servicechannel, to delete a Program Identifier (PID) of a lower neighborservice channel and add a PID of the upper neighbor service channel ofthe new ongoing service channel and controls the broadcast demodulatorand the storage unit, if the standby service channel is the lowerneighbor service channel, to delete the PID of the upper neighborservice channel of the ongoing service channel and add the PID of thelower neighbor service channel of the new ongoing service channel. 7.The mobile phone of claim 6, wherein the controller controls the storageunit to read out, when the ongoing service channel is switched to one ofthe standby service channels, the buffered broadcast data of theswitched standby service channel, and resets the broadcast demodulatorand the storage with identifier of new ongoing and standby servicechannels.
 8. The mobile phone of claim 7, wherein the controllercontrols the display to display, when an incoming call is received inthe broadcast mode, an incoming call alert message with callerinformation on the display.
 9. The mobile phone of claim 6, wherein thecontroller controls a radio frequency unit to transmit, when an outgoingcall event occurs, the outgoing call through an antenna.
 10. The mobilephone of claim 6, wherein the standby service channels comprise channelshaving a higher probability for selection as an ongoing service channelduring a subsequent channel switching.